I recently saw a Wikipedia article talking about five different ways a word can be used. Unfortunately, I can't find it right now. Some of the different uses of "head" are:
- Literal: a literal head with two eyes, a mouth, etc.
- Figurative: a head of lettuce - not a literal head, but roughly the same size and shape
- Functional: the head of an organisation - as a head controls a body, so the head of an organisation controls the organisation, the leading part
- Positional: the head of a queue - the front, the foremost part
So, for a demon to tiptoe doesn't mean it has to literally have toes. However, perhaps your demon is so pedantic they refuse to accept any definitions except literal ones. In that case they might coin awkward or humorous alternatives that more literally mean what they want to say.
They could see "to tiphoof" as an alternative to "to tiptoe" to only be used for hoofed creatures, or they could have been using it for so long that they don't even realise that "to tiptoe" is a correct word! It depends how much humour you want in your story.
Terry Pratchett is a good example of how characters can be internally serious (they consider themselves serious and dignified), but are portrayed as very silly to the reader. If your story is intended to be serious, it will be much harder to pull off, as the nonstandard language will distract from a serious story, while it would enhance a comedic story.
It also depends on what form the demons' correctness is manifested. Do they insist on correct English (or whatever language they use), in which case "tiptoe" is correct and "tiphoof" is incorrect, or do they insist that all words have to mean what they appear to mean and can't have figurative or idiomatic meanings? Ultimately, that's up to you to decide.