I asked them a question about conversion, and while they said some owners do it, they do not reccomend it, so they did not offer any useful info.
I have landed on the opinion that if I want to shoot a different caliber from one of my pistols, I will get that caliber piostol.
I suppose it's fine to change out barrels in a pinch (in cases of ammo shortage), but for me, I'm gonna keep the caliber pistol laying around so that it's dedicated. I.e. I'm beginning to want .357 and 10mm. I had been wondering if I could switch barrels in one of my 21's to shoot 10mm. That was when I called to ask ehte question. They did say there were aftermarket companies who do this, but not rec'd by Glock.
Tim, your anecdote isn't really germane to the OP's question, as the 10mm/.45acp conversion was/is unique. Dropping a factory .357 Sig barrel into a Glock .40 isn't really a conversion, I suppose. However, conversion barrels such as the LWD, etc., .40-to-9mm work fine.
I got sucked into the .45ACP to 10mm conversion barrel scam. I tried around 1000 rounds, trying different "tricks" in loading, filing extractor pads, etc., and never got reliable extraction. The fact is, there's no extractor tension on the 10mm case, using a .45ACP extractor, and the 10mm (G20) extractor won't fit in the G21 slide.
I've fired over 10,000 .400 Cor-Bons and over 3000 .40 Supers through G21s, with reliable function ONLY with 10-round, Klintonista mags.

The best two groups that I ever shot with one of my handguns at 100 yards were two sub-5", five-shot groups shot through a .40 Super barrel in a G21.