Any suggestions on how to bypass the question of past/expected comp then?
I have been on interviews where this is part of a boiler plate release/waiver for a background check, prior to receiving an offer letter, and on the same form, you are made to list prior employers, and fill in the salary box for each.
And if you don't like it, good luck taking legal action, right? Whether something is legal or illegal, most people lack the resources to even entertain the idea of challenging legality.
The only path that seems to effectively buffer this practice is working with recruiting agencies, which do a better job of negotiating, but do still collect this information. And although recruiters might only be capable of telling you whether you have real leverage for your salary demands, whether the recruiter is being paid by you or the employer is a clue as to who they're working for.
Hint: if you aren't paying them out of pocket, recruiters aren't actually working for you, even if they seem really pleasant.
Then again, I'm fortunate to have highly sought skills and years of experience, but I wouldn't go so far as to say that's the only way to get fair pay.
Edit: I should point out that I'm not making anything to brag about by silicon valley standards, but I also live somewhere with much, much lower cost of living and salaries in general, and make the high end of what's common out here.
2. Make up a figure -- you have a lot of leeway to do so truthfully by adding or not adding various benefits to the number you state.