It does have the same problem as using a laptop as a server: the battery will fail. But it's a nice UPS until then.

A lot more mobile devices will require removable batteries after 2027 due to EU regs.

There are exceptions, so not all phones will, but more will. I hope there'll be more time/effort put into hacking removable battery phones to accept hardwiring a PSU onto the battery terminals over the next 5 years.