The 9mm is a high pressure round, approx 30,000psi, similar to .40 cal.
The 45 acp is a 19K psi cartridge. If double charged....probably closer to 40,000psi?...my guess is as good as anybody's. The 1911 is not designed to handle kaboom level pressures, although I heard that proof tests are done at twice the normal pressure.
Anyway, many believe the G22 kb issue is due to less case support in its chamber.
I believe this is a CYB (cover your butt) warning by Glock's lawyers. I have shot a few magazines of lead bullets through my G17. No issues with leading. If you want to shoot lead, try one magazine at a time. Check your bore with a borelight so you clearly see the rifling or the lead fouling.
Read other forums and you will see some Glock shooters who shoot 2-300 rounds of lead bullets through their polygonal barrels and no kaboom or harmfull effects. The key is keeping the bore as clean as possible. If one knows the "limits" of his Glock and understand bullets or reloading them, it should be ok to shoot lead, but if anything bad happens, your SOL.