In a previous version of the ST Android app (April of this year), if you didn’t have the Contacts permission allowed, you would be forced to login to SmartThings after a period of time, the next time you opened up the app.
See previous thread on this and posts between April 28th and May 3rd. I specifically tested the OPs scenario and could reproduce it at that time under that version of ST.
So if you end up with whacky behavior because you don’t want to allow the Contacts permission to be allowed, you will have an idea why.