I have had an iOttie vent car clip for over five years, and once I got it in the right spot, it has stayed onand held my phone securely. I can’t remember the last time it came out of the vent. I have it clipped in towards the bottom, so the vent itself can’t swivel, but that’s it.
If it were magnetic, I wouldn’t want to replace it even now.
I know there are definitely some badly designed versions out there, so I can see how some might skip out or drop the phone, but mine was only like $25, and it’s been perfect.