I think that's too strong. The underarm ball was a case of playing within the rules, but against most people's notion of fair play. The hand of god would fit most people's definition of actual cheating.

It was actual cheating by even the rules of the game, just the referee didn’t see it.

I think I agree, but I hedged because I thought one could argue that it's not 'cheating' in the same way as, say, sneaking into the scorer's shed and writing in an extra goal would be. A deliberate handball is 'just' an in-game action that should have been penalised but wasn't (due to referee error), and deliberately breaking the rules isn't always considered cheating. For example, basketball and soccer both have their own version of the 'professional foul', and even in soccer where this earns the player a card, it seems to be considered an accepted tactical trade rather than cheating. I don't think this argument really holds up, though, because the hand of god goal depended entirely on getting away with the rule breach, whereas professional fouls involve getting caught and accepting the consequences.