> but part of the point was to allow candidates to gauge their own abilities and not waste their time interviewing without a chance of being hired.

In my experience this is the wrong game theory. Unemployed people can make job hunting their full time job, so a 20 minute take home doesn't select for "who delivers the highest quality solution in the least amount of time," it selects for "who is the richest applicant who can burn hours on a take home to deliver a higher quality result than people with less time they can afford to spend?"

Also, nobody should ever self-select themselves out of an interview process. Passing a resume review and getting a callback is about 10% likely: for every job hunt, in my experience , candidates get about 10 callbacks for every 100 resume sends. From there, it's about 20% chance to get to final stage, and from there, maybe 50% to get an offer (you're either their first choice or second; if second, your hiring hinges on whether the first choice accepts). Math is right there: once you pass a resume check, in terms of the volume of applications you've sent, it's optimal to spend far more effort into this gig than into firing off ten or twenty more resumes.

Therefore, even if the candidate doesn't think they're a good fit, they should do everything they can to stay in the game, including lying by omission.

After all they might be engaging in imposter syndrome, right? Why assume for the interviewer that your python skills aren't good enough - maybe the interviewer understands perfectly well that you've only used it for scripts and one off tools, but doesn't care because they personally believe your startup experience is more valuable to them and they believe you can up skill! Maybe the take home was designed poorly by someone who was tasked randomly by a lead to shit out a take home, and it's not an accurate indication of what the job would be like. Maybe they sent you the wrong take home? Maybe it's a good take home but you need money so fuck it, if you manage to sneak in despite not being a good fit, you can just bust ass to upskill and make up the difference before anyone notices. Or fuck it twice, it's a shit market and who knows how much longer you'll be able to sell your labor as an engineer, even if you can only fool them for two weeks, that's two weeks of income while you still keep up your job hunt.