Reeling back a fishingrod even though it isn't hooked on the entity while being close to that said entity, subtracts the duribility.

If the durability it loses is 2 then it is very likely caused by MC-98922

The problem is that the xTile, yTile, zTile and inTile are not updated, however it tests if the the block at this position is the block stored as inTile if it is inGround. If this is not the case (which always happens) inGround is set to false because it assumes the hook moved. This durability reduction is because the hook is inGround.

I believe fishing rods are supposed to lose durability when ever they are used.

That is not correct. The Wiki lists the correct amount of durability used, however here is a table as well.

Intended. The bobber is in the ground when you reel it back.