Comparing pictures from the factory and historic ones, is that age[1] or illness or... someonething else causing the jowelly differences? I mean, how long can they have to search for someone who looks sorta-like him in the event of ever needing one, given that Saddam had a brace or more moustachioed lookee-likees on his payroll already.
To his people (not in on the plan) a mixture of credulity, loyalty and fear might be enough to let them use someone roughly of the same appearance, with a new Supreme Leader Haircut №1 if he didn't already have that one from the Approved List before being officially appointed.
Though, if they wanted to do that, they obviously failed, given that I've got more-than-a-suspicion about it.
I suppose it might be whatever it was that kept him out of the public/international eye for this period of time that could have changed him. Too much bed-rest and/or a minor but bruising face-lift and/or a change in diet/etc. But who knows. Well, I'm sure someone does, in Pyongyang or a Letter Agency regional department at the very least.
[1] I'm not as familiar with how the oriental face ages, as one closer to home might, and even then I'm far from a forensic expert.
(Obviously if I were to say that %Random_Ethnic_Person_1% looks indistingishable from %Random_Ethnic_Person_2% then I might be saying something with at least a hint of racism to it. I think I'm on safer ground potentially saying the complete opposite, but still a little self-conscious I might be falling into a very similar kind of trap.)