It makes sense in the abstract: e.g. imagine you're accused of murder, and you know someone saw you somewhere else at the supposed time of the crime, yet they refuse to provide evidence to help you. It would seem reasonable they could compel you under that circumstance to testify.

Since the FTC has initiated a court case against Meta, I assume they are provided a similar legal right to command competitors to provide evidence that they haven't behaved "anti-competitively".

The question becomes whether, in this particular instance, they're abusing that privilege by demanding information they shouldn't be entitled to from unrelated/extraneous parties.