Contra has a primitive gameplay (like the basic movement/jump design), so the complexity of interaction is lower, and a couple of boss fights I've watched is literally moving the player in 5 different positions and just shooting around, maybe with a couple of jumps in between, so also nothing as complex.

And a sequence of 30 bosses is too spread out to be comparable to a single condensed boss fight.

Besides that, I don't knows how buggy those bosses are, so can't compare how much of the difficulty is positive

But in general, it doesn't have to be different? The author describes a common principle of separating "good/rewarding" difficulty from bad, any game can be improved by removing invisible hitboxes that frustrate you...