Sadly the whole connectivity thing is something most companies have been dreadful at. Renault/Dacia has a very patchy app which probably only communicates successfully with the car (Zoe originally, now Megane) about 30% of the time. Most of the time it simply times out and they are too hopeless or disinterested to fix it.
The Stellantis group cars are legendary for having the absolute worst app and connectivity, with even most YouTubers and reviewers failing to get their cars to even pair to their phone's app and account. This is one of the main reasons I'm not buying a car using the Stellantis platform.
The Polestar app was pretty flaky at first as (it turned out) it was using the same connectivity provider as Renault! They switched about 2 years ago and after that, it was generally extremely reliable.
However by far the best has been the VW system. Our ID.3 app works flawlessly 99% of the time.
The "don't drain the 12V battery" thing is a partial myth / excuse by the manufacturer/dealer, as all EVs monitor the 12V battery from time to time and do a top-up charge from the traction battery if required. However this doesn't work very well on many cars, hence the sheer number of 12V battery problems reported on forums, particularly EV forums where we have active connectivity systems, over-the-air updates etc, which require some electronic control units to remain powered up the whole time.