Were you using an exit node? Because that really does hammer the battery, but vanilla TS without a bunch of traffic doesn't seem to do much to mine.
The only always-on TS service on my phone is Immich for photo backup, and I don't take enough photos for that to matter much.
You should compare battery consumption of TS exit node with something like WG app which low
I wasn't, no. I'm not the only one whos hit it either, not sure what the cause is :(