Yasuo Otsuka's rock-man scene from Horus is one of the early great examples.

https://sakugabooru.com/post/show/22968/animals-animated-character_acting-creatures-debris

As it says on his Anipages entry (http://www.pelleas.net/animators/) he animated the giant on 3s to portray the huge size of the character. In many ways frame modulation is an offshoot of anime's limited budgets but it also allows for more dynamic action scenes rather than everything flowing at a constant rate.