wriggle might be referring to pool #539, more specifically post #482969 and post #489236 though those are very late in that comic series so if you want to avoid spoilers, read the whole pool first if you want to.

EDIT: but ya, could be making fun of power vagueness like said.

I can't help but to wonder if it's also making fun of how ZUN describes abilities (and incidentally, how some western fans translate the bits as)

Wriggle said:
Show me the limit of the ability to the extent of controlling flowers!

That's quite a mouthful.