Well, that's like... a whole different situation. Why wouldn't you mention that ?

Unfortunately lying is the correct response here.

Oh, that's different, IIUC, if an employer asks about a history gap, and the candidate volunteers the information "I had kids," they can take that into account.

The system's broken.

None of that matters. An employer is free to ask any questions they want.

What they aren't free to do is make discriminatory hiring decisions based on membership in protected classes.

Avoiding asking certain types of personal questions is one way to avoid the appearance of discriminatory hiring practices.

>they can take that into account.

They can't take that into account just because you bring it up. Whether or not you bring it up or they ask doesn't matter. Some jurisdictions have laws explicitly forbiding discrimination against parents, and the federal prohibition on sex discrimination means that discrimination against caregivers is generally prohibited (since women are more likely to be caregivers, discrimination against them is defacto discriminatory towards women)