That sounds much, much worse. I'd take no SD card support at all over having to explain to people why, when they take their card out of the phone and put it in their camera, their phone shits itself.
The last phone I had that did this was an old Samsung Focus, and Samsung was very quick to point this out at every step of the way. The emphasize in the manual very clearly that this storage is a permanent addition, not a way of removable storage.
Is it any different from telling people if they unplug their desktop's boot drive, the computer will stop working?
People don't have an expectation of hard drives being removable(most people probably don't even realize they can be removed), whereas SD cards are explicitly designed to be mobile. People treat them as mini USB drives, so this behaviour is directly counter to most people's intuition, regardless of its technical merits.
What are the numbers of people swapping their SD cards out of their phone and into something else (and expecting it to work)? I don't know the statistics, but I'm willing to bet it's low. In fact, the number of people in general putting SD cards into their phones is likely to be very low, since a lot of phones don't support it.
I really don't understand your argument that phones just shouldn't support SD cards rather than having the option to expand the storage for cheaper than buying the next model up just to avoid user confusion. If every phone locked out useful features just for the sake of avoiding user confusion, Android wouldn't exist.
Is it any different from telling people if they unplug their desktop's boot drive, the computer will stop working?