Yes, that's entirely possible. My comment was made keeping in mind that the scientific norm is to have a single preregistration for a single experiment. If a researcher wants to test N hypothesis, using an appropriate p-value correction to account for this, usually the entire set of hypotheses and the correction itself would be contained in a single registration. And that would be perfectly fine.

Submiting a large number of individual registrations for a single set of data is just not the norm and so it would be suspicious to begin with. (Okay, I will admit that on the order of 2-3 registrations for very different categories of study may not be as strange; but certainly 20 would signal something very odd).