Bay 12 Games Forum

Hmm, so what I'm getting from this, is that the actual generation parameters from the temperature map (the ones I turn off in PW when the temperature map is selected on the parameter tab) are not subject to the same limitations that the pre-set map data is. ...

That's my understanding, yes.  I don't know if it's intentional or a bug, but that's exactly the behavior. 

We can't set the temps outside a limited/capped range (that specifically is NOT lethal), even if you use a pre-set-values map.  However, if you use poles and set the temperature high enough or low enough and let the old (pre 0.40.9) pole behavior produce the gradient, you can get lethal temperatures.

Short version; with poles = potentially lethal temperatures.  without poles = ~always "friendly" temperatures.

Another interesting behavior I noticed when testing this... if your temperature is high enough or low enough, on the embark finder, you'll get the "NO TRADE" warning come up.  In the past, that would prevent trade caravans from visiting.  Currently (at least, in 0.40.12) this is no longer true, and Dwarven Caravans visit (and suffer cold damage, at least) regardless of this setting.
This has the consequence of causing potentially tremendous damage to containers, resulting in carried goods being.. "liberated" or destroyed from the caravan while they're on the surface.

Also, if the temperature is high enough or low enough, no animals of any kind will visit the embark surface.  This, too, has some interesting possibilities for certain challenge forts.  Even though animals will not visit normally, though, currently this doesn't stop the dwarven trade caravan.

You may already know this, cephalo, but the 'pole' settings determine whether or not you can go over/under temperature for things like cold damage and melting body fat, etc. 
Without them, as you've surmised, you can't exceed certain limits, but with the poles in play, you can romp in the danger zone.  Not sure if this is something you want to deal with, but it's a possible feature.

I seem to gen a lot of worlds that have no lignite or bituminous coal for forging.

Current world gen has none on any squares.  And that means 1 for 1 wood use for a forested area.  There is a volcano but no wood. 

The concern is that there are two civilizations showing but one has just 1 square and the other appears to be dead. 

Is this just bad luck in genning a world?

Not really bad luck.  As per the wiki, Lignite and Bituminous Coal are found in sedimentary layers.  Volcanos require igneous extrusive layers.  They are often mutually exclusive in DF, that is, it's rare/challenging/difficult to find them in the same embark tile.
The lack of wood is caused by low rain, low drain.  Increase rain/drain, you'll have (yes, literally) thousands of logs available on the tiniest embark.

With multi-tile trees on even a shrubland embark, there's often so many logs, it's absurd/ridiculous/comical.  To say nothing of a temperate coniferous forest or tropical moist broadleaf forest.

Finally, people often want a volcano so they can use magma forges.  Ok, fair enough.  You can also build magma forges on the magma sea.  It is trivial to generate a world with magma within 20 Z of the embark level.  It's often closer to dig straight down 20Z than it is to build a magma forge on a surface volcano, which are almost always more than 20 steps away, on the surface.
Point being?  If the point of the volcano is to have a magma forge, you can achieve that goal faster & quicker with a shallow world.  The best part is, without the need for a volcano, you can reduce volcanism to zero and generate 100% sedimentary worlds and get all those tasty things like iron bearing ore, 4/5 OTHER kinds of flux, and coal and lignite by the thousands. 

Then you can focus on fun things like finding embarks with all of that PLUS adding large amounts of bauxite, kimberllite, and similar for rare & precious stone generation. 

... Oh wow, awesome. So all I need to do is channel down into a partial aquifer (which I have) from one square directly above said aquifer?

Yarr.  Then enable Zone-Only Drinking (o,z,d) and designate it as a water source. (i,enter,enter,w) 
Build a well on it if you don't want "lack of a well" complaints.  If you do build a well, you can remove the water source designation, it's not necessary once a well is present.

If you don't want them on the surface, a partial aquifer embark may meet your needs.  Channeling into an aquifer from above provides an instantly secure and forever clean fresh water source.

Re-tested this in 40.12 just now.  Three years from cavern pierced on muddied stone, deep below ground, to new bloodthorn mushroom trees.  17 Sandstone year 100 pierced the caverns, saw trees just before 11 Timber year 103.

Going to re-test with smaller mud area to see if it's related to sapling density or just time passing.

EDIT:

Same results with a single sapling;
Sapling sprouted 15 Slate year 102.
Mushroom Tree (Bloodthorn) matured from sapling 21 Granite year 105.

So, growth is apparently not related to sapling density, as that was the only sapling in a 41x21x12 open area.

Can I get a world with-
 ...

I believe this matches everything but the cassiterite:
Three biomes in a 3x2:

• Warm Temperate Shrubland, Mirthful
• Warm Temperate Grassland, Joyous Wilds
• Warm Temperate Broadleaf Forest, Serene

There is an embark in the world with cassiterite, but no limestone, although still some flux.  If the intent of the Limestone is for flux, that one might be better.
Also, I managed to get 4/5 types of flux, in this one embark.