
While I've not come up with a specific case which inevitably needs them, still I think they're a bit more useful while playing with an extremely modulated FM module or a modulator. They often sound quite a different note from the actual one or sometimes sound atonal, and tweaking their finetunes drastically changes their sound, which I think is apt for Dubstep or other music genres welcome with those weird sound.
The two commands probably help you avoid changing a note's transposition by inputting a new note or opening the transpose dialog, while tweaking a module's pitch beyond finetunes in order to generate such sound.