You are right about tpu.
Pla is bio degradable under certain circumstances (in industrial composters).
And even if it gets softer in hot temperatures, I don’t think it will melt in your pocket.
I don’t know what rim protector you are talking about… (And I don’t know what it is to be honest… and english isn’t my native language…) But I don’t think an industrial product will be made in PLA.