This too. In all the other bosses, Eggman is a relatively small target that keeps moving around, and you have to follow and leap after him. If you need to grab dropped rings, you've got to get them quick and get right back to keeping up with Eggman's pattern. In the Death Egg boss, his big weak spot is right there in front of you, just guarded by his hands. If at any point those hands weren't a threat, you could instantly smack him two or three times in a row with little effort. Plus, it makes sense from a narrative standpoint. Sonic's cornered on Eggman's home turf by the most powerful robot yet, and he's without his only source of protection, but he's still got to win somehow, there's no way to give up or turn back now. It is certainly something an easy mode could alter, not really too different from how Knuckles is already hard mode due to his short jump, but I think the Sonic 2 last battle is a great thrill the way it is.