I pulled out my gun to check on this. if you slide in a mag, it stops at about 10mm from full home. then there is a notching where the mag goes in another 8mm. I can feel the mag release moving. the magazine can still be pulled out without using the release. Then one final push seats the mag and it is locked.
if you do the same with the slide locked back, the mag still catches the mag release at the 10 mm mark, but then goes directly home and locked in after a small push.
since I am a lefty, I tend not to use the slide release. So I say, slap it home and slingshot it.