A lot of people remove the magazine disconnect to improve the trigger pull and for other reasons. A "previously owned" Hi Power may have had that done.
Some say it is an advantage to be able to remove the magazine, leave a cartridge in the chamber, and have the firearm be unfireable. Some say it is not an advantage.
Have never tried it. May try it just to be sure. I believe mine may have been modified even though I bought it “new” from a local, brand name, sporting goods store.
It has a very light trigger pull when compared to my friends hi-power. Takes some getting used to. Was going to have a gun smith look at it. Might have been modified as you mention.
Bottom line: I won't count on it. Just curious.
Rule #1: always treat a firearm as if it is loaded.
The one scenario I can see where it would be an advantage would be if a crook was grabbing one's weapon and one had a backup piece. In that case, drop the mag, let go of the gun, and shoot the crook with the backup gun before the crook can restore his newly-stolen gun to function.