As of 6/21/2022, this bug has been fixed in TF2. https://www.teamfortress.com/post.php?id=139819
A quick attempt at fixing an exploit(?) with the load_itempreset command
This is a lame attempt, but it works, it would probably be more efficient to patch the memory for this function.
The inspiration for this comes from this discussion, https://forums.alliedmods.net/showpost.php?p=2777610&postcount=5.
Sure enough, forcing the boolean value to true in the PointInRespawnRoom function called in CTFPlayer::CheckInstantLoadoutRespawn will ensure that a player must be on the team of a respawn room they are inside or touching.
This is meant to fix an issue that occurs on certain maps where an enemy player can "touch" the resupply room, which allows them to run the command and instantly respawn in their own spawnroom. This is done to spawncamp usually.
As an additional note, I also tried using the m_iSpawnRoomTouchCountas a way to determine if a player is in their spawnroom or not but that too isn't checked for team ownership correctly.
# This requires dhooks
Credit for this goes to nosoop and Psyk0tik, I just wrote out code for it.