Unfortunate but that's what they do.
They'll actually send these modders an email expressing interest in the project and ask them to tell them everything about it (to gather legal evidence). Once the modder responds Capcom will send a second email warning them of copyright violations and unless taken down they will indeed take legal action.
Capcom is not very modder friendly. Not saying that's a good thing or a bad thing (I myself very rarely use mods and for the most part only do when I absolutely have to) but it is what it is.