I would argue that it's a dark pattern if that's the only way past the form.

A lot of sites using that technique also let you click an X button or click the darkened non-form area to continue. If that's supported, I always choose it as a tiny protest (in hopes that someone actually profiles how click-outs are happening).

If you make users click something obnoxious and self-deprecating to continue, then I'd certainly call that a dark pattern. It's like an incredibly mild version of the cult tactic where you shame people for skepticism.