Bashing granite with lead may sort of work, but you're gonna damage the mace more than the rock. You're right, it may make sense to give a slight advantage to the pick material, but I don't think bashing granite with lead is realistic. Maybe if weapon wear were implemented.
It's extremely realistic if all you have on site is lead furniture to melt down, and a kea flew off with your only picks. Or if you want to cut something harder than anything dwarves have invented to make tools out of.
Are the dwarves going to say "Oh well, the nicest, most convenient tool isn't available, so I guess we will just sit here and starve to death" or are they going to say "Well shit, I guess we will have to make a big stupid lead hammer and spend 10x as long smashing the rocks apart until we can get something better." ? They're gonna choose the latter.
Civilizations throughout history have made huge, precision-cut monuments using tools that were softer than the rocks they were shaping. In fact, I'd go so far as to guess that cutting rocks with things softer than them has been the norm for our species in general, not the other way around.
Air and wind may help erode mountains, but those aren't the same forces at work as heaving a pick. Canyon are more often formed by the eroding effect of water.
Yeah, they don't work the same way a pick works.
...So what? If the way a pick works isn't going to get the job done... don't use a pick. use the things that DO work. This is the suggestions forum, you know. One of the changes related to mining velocity could be using and needing alternative tools that work differently or more quickly than pick technology if you don't have the right metals on hand.
A high kinetic energy hammer is one method. A more common historical one is something like getting wooden rotating poles, grinding holes into a rock with sand/grit, sticking wooden wedges in there, then soaking them with water to expand them and create tremendous pressure that splits the rock. No metals are even needed at all (though they do make this process easier too)
I think it's also often possible to use bonfires to heat some kinds of rock so they expand and crumble into useable chunks.