I don't see anything in the Glock manual for my G20 that says not to. I'll get in the safe tomorrow, and load it up just to see. I can't remember having any problems with function, or accuracy with any of my others that I carry. S/A XD40 Subcompact, Ruger LCP. or KAHR CM9. Also a CZ82, and E.German Makarov that have served as "truck" guns in the past. All function tested, accuracy tested, and carried full +1.
I guess if it's a matter of if a full mag goes in OK with a round in the chamber, and the gun functions properly loaded that way, why not!
Cheapshooter's rules of gun ownership #1: NEVER SELL OR TRADE ANYTHING!