I have also done this trick a few times with good results, once unsuccessfully, but that pipe was so far gone I didn't have high hopes to begin with lol.
@AlphaWarrior offers sage advice about how soft those metal screw tenons can be. I would first find out if the tenon was meant to be repeatedly user-adjusted by twisting the stem in the pipe (ex. Kaywoodie's "Synchrostem") and is now seized from dried gunk, or if the alignment is meant to be permeant and the tenon was glued or friction fit into the stem. Seized adjustable tenons usually only need a quick clockwise twist of the stem in the pipe to free it up to rotate and don't require much, if any, heat because all you're doing is breaking up some dried up tobacco juices.
For production pipes made after the 40s-50's it's most likely an adjustable screw tenon, and in my experience I've never had an adjustable stem so seized that it required heating above room temperature to get it to break free. If you want to be really careful you can smoke the pipe to warm it up before twisting it.
With a permanently attached tenon, you have to heat up the metal tenon enough to melt the adhesive they used to attach it inside the stem, or overcome the friction fit by melting the stem material around the tenon, without melting the stem itself. With this method you can't just heat up the tenon and twist the stem in the pipe until it's straight because you run the risk of the threads pulling the hot tenon out of the stem or at the very least warping the stem's shoulder.
It's probably a safe bet to say a medico screw tenon would be adjustable but anecdotally, I collect old American drugstore pipes and have around 20 Medicos, but I can't remember ever seeing one with a screw tenon. Looking at the ones that happen to be near me (5 pipes: 1 Crest, 2 V.F.Q., 2 Gold Crest) and they are all push tenons. It's probably just my bad memory because I haven't studied up on Medico's for a few years, but I would love to see a picture or two of the one you have!