Free transfers have been abused to mule resoures for over a year in Classic Era:
https://us.forums.blizzard.com/en/wow/t/classic-era-exploitation-of-free-transfers/
I’ve been calling attention to this in these past 3 ‘This Week In WoW’ blueposts. No response yet.
The users exploiting resources of low-pop Era Realms and shuttling them to free Xfer destinations are already established. They have no reason to branch out to the HC realms. That would just be adding unnecessary work.