I don't think the issue is his head; the arms are too big.
OMG that looks amazing!!!
The issue is Bunsen and Beaker's arms are switched around... literally. I honestly have to believe this was an error in painting and assembly, because Bunsen's arms are also too skinny.
Animal's drum set and the balcony are exciting; both two of Palisades' rarest mistakes/omissions. I was always kind of disappointed Palisades Electric Mayhem playset really didn't bear much resemblance to the show, but they hit the nail on the head here!
Awesome.
These can easily be nit-picked to death, but the real answer is...there is no real answer. I think some people think of the previous figures as accurate when they're actually just one more interpretation of something that's difficult to pin down. If the arms were to be exactly on puppet model, they'd look long, thick and gorilla-like (a lot more so than what we see in these prototypes).
Beaker and Bunsen are "live arm/hand" puppets. We fanatics know that means their arms and hands are gloves that fit human hands inside of them. They don't connect the same way on the poser versions of the puppet. Those tend to look skinnier or sometimes thicker.
Beaker has baggy sleeves. These may have translated a little bulky, but not much bulkier than the production puppet. If anything, Bunsen's arms are too thin, but they do match his poser. I think people will forget about most of it once they start playing with these and posing them. But I can say with a moderate degree of certainty that the arms were not switched in production. That's not how design like this works. They simply wouldn't fit.
I'm so glad to hear the reviews of Animal, Statler and Waldorf. All very 70's retro. That Waldorf is very much Jim Henson's classic Waldorf and I love the stuffing out of that crotchety old fella!