It's a good point. The reasoning behind the moves matter. There's a huge difference between switching jobs because a better opportunity is available, and switching jobs frequently for lateral moves.
It would probably be more accurate to say that it's a yellow flag, requiring a bit of explanation but not necessarily a bad thing. I find the pattern of switching every 6 months for (presumably) ~10 years to be pretty extreme and difficult to explain, though. Not to mention exhausting! How many job interviews must that have taken?
No kidding! Here I am complaining about 18-24 month moves and the OP was moving in 1/3rd to 1/4th of the time. Whatever uppers he's taking can't be good for you. Either that or he has the best spouse in history.
Still, honestly, it's a yellow flag. If the guy is good, 6 months may be just fine. But it's a cautious interview I'd think.
It would probably be more accurate to say that it's a yellow flag, requiring a bit of explanation but not necessarily a bad thing. I find the pattern of switching every 6 months for (presumably) ~10 years to be pretty extreme and difficult to explain, though. Not to mention exhausting! How many job interviews must that have taken?