Do you have favorite examples of framerate modulation use? Could you post some of them and describe a bit how you feel about it and why you like it? If you know a bit about the subject, I'd be interested to read what you know about the approach, what is the main idea behind framerate modulation, using the exact minimal number of drawing for a movement/series of movements, all while keeping it the most effective, readable, believable possible?

I don't know but it seems like an art in the art and it's kind of animation optimization only in thought form since you're not drawing beforehand and dropping frames (like with CGI that emulates 2D, KLK), I find this interesting. I'm also intrigued by the fact that some says it's unique to Japanese animation (or born from it) and absent from classical Disney. Wouldn't the approach of tweaking the timing to minimize the amount of drawing while keeping it effective be kind of a given, if 24 drawing per second are useless? Drawing is hard...

Well I could write a lot of questions and reflections about the matter but I'll keep it to the first paragraph, ignore my Disney part unless you're really interested in the discussion, but it might go round fast since I don't know any real answers.

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.