That's... iffy. A fundamental rule of magic is that Drain can only ever be healed naturally by resting, not by any other magical or mundane means. A GM might rule that you're not really healing so much as transferring the box of damage to the target, but if so this would be a majorly broken ability (any Mystic Adept could heal up all of their physical drain damage after a battle just by punching walls and furniture until it was gone).
"Iffy" is not the same as "explicitly forbidden" under RAW. Transfer Damage specifies "physical damage". Last I checked, physical drain does in fact cause physical damage.
It's interpretative. Apply where you find appropriate.
That said, I agree as a general rule that Drain damage normally shouldn't be transferable or easily healed...NORMALLY.
So at my table, I'd probably frown on this interpretation or reserve such an interaction for practitioners of blood magic or any other tradition that is explicitly about taking life to fuel one's magical power.
Mainly because such traditions carry consequences for their methods. (or ought to)
The biggest concern I'd have is out-of-combat scenarios.
Rituals, Channeling, Quickening, or any other big-drain magical investment. The practitioner would need willing subjects or more likely, unwilling victims to transfer their drain onto.
Which again...isn't out of place for magical traditions like Blood Magic.
I mean, it'd make for a seriously dark scene where someone literally bludgeons some poor schmuck to heal back and continue with the process...but yeah. Probably not something I'd want in my PCs' hands.
Looking at the practicality of the power outside of blood magic shenanigans.
It'd certainly be risky since it requires the Mystic Adept to be:
1) In melee striking range
2) Already injured (and thus taking penalties)
If they screw up their little combo attempt, they are probably going to die.