Thrown Arm Master is an interesting feat from the Tal'Dorei Campaign Setting Reborn, but I'm curious about its interaction with the Returning Weapon infusion. Namely the following part about Thrown Arm Master:
Simple and martial melee weapons without the thrown property have the thrown property for you. One-handed weapons have a normal range of 20 feet and a long range of 60 feet, while two-handed weapons have a normal range of 15 feet and a long range of 30 feet.
How does this interact with the returning weapon infusion? Since its prerequisite calls for the following:
Prerequisite: A simple or martial weapon with the thrown property
While understandably the infusion doesn't apply to weapons that don't have it by default such as Battleaxes or Greatswords, the feat specifically adds the thrown property to weapons that don't have it. Not "You may throw this weapon" semantic loophole that allows you to throw it but not make it a thrown weapon, but specifically gives weapons the thrown property.