I've done whiteboarding once. It wasn't the worst thing ever, but after the last time I did it, I did put that company on my "never work for" list.
C2H here at least is through a staffing company who (for me) have provided benefits on day one. My oldest was born while I was in this arrangement. I think contract (as in benefits or no) in most cases came down to a startup wanting to hire me (the types who thought 48k USD/year was "a lot")
My current job did this, and it was infuriating. The whole process lasted a month with lots of last-minute changes in schedule ("Can you come in like 6 hours for another interview?"). I let it slide since it was an old boss of mine who wanted me to work with him, but I've done some interviews since, and this, #4, and #7 get that company instantly on my blacklist.
I hate these. I'm surprised you didn't mention Amazon's asinine "bar-raiser" interviews that are functionally this (even if they claim it's to do what you suggest). I have to admit though that I don't really believe in "company culture," and in my experience it's used in conjunction with #10 to discriminate.
Surprisingly, I didn't go through these when I interviewed at Amazon. Not self-taught, but not a CS grad and certainly not from an Ivy or "Public Ivy." I've only heard group interviews like these when someone's pitching an MLM/pyramid scheme.
The company from #1 (who tried competing with AWS) and Amazon did this both. Both required out-of-town (driving to another city an hour away and flying to Seattle) travel, and I couldn't tell you anything about the experiences other than how bored I was.
Every company I've mentioned has done this. I purposefully gave the most ridiculous answers (ones that would show I have no plans to stick around) and... still got the job.
This is probably more reasonable to expect in a startup. A corporation you're lucky to get a VP-level executive (I've only had an non-startup executive in an interview at my current job.). These, however, have proven to be very telling. They almost immediately give away the pros/cons unintentionally.
Yep, I don't think this has ever come up beyond maybe the HR screen.
I don't have reluctance to these, but since I'm looking more for remote (or ideally just freelancing) work, the red flags you gave definitely would give me pause.
With that said, that is by and large why I've lost a taste for software. I can do/tolerate it in certain scenarios, but I couldn't be a software engineer ever again, and I think so many companies are on my "never work here" list that the only option is self-employment for me. It has it's challenges, but I at least can control them. As a guy just working somewhere what I lose in exchange for a salary is worse than what I gain from flexible work.
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