That said I've only used the wired bullet cams so maybe other models are not so nice.
Really the only downside I've seen is about 5ish years ago, all the bullet cams I bought would die after about .75 -> 3 years. All died with the same issue and I had 100% failure rate with any bought during that time frame. Ubiquiti replaced the ones that died during the warranty period but most died just after that expired.
The ones bought before or after that have been great so the issue was solved but I have a nice stack of dead ones that would work great as fake cameras, especially as their IR leds still light up.
The cameras and viewports should not be writing data at all after an initial configuration if designed properly and killing power should present no problems to any system with a read-only filesystem. As someone who designs systems like these it absolutely baffles me.
The UPS remark is such an non sequitur. Sure, it's prudent to have one but this doesn't make the bug go away.
The cameras should reassociate almost immediately after regaining a connection. It shouldn't take hours for them to try and connect again. I won't fault the camera for going down when the power dies, I will fault it for not coming back immediately after the power comes back though!