Actually, it's not a slide release lever;
It's a slide LOCK lever;
You're right -- that's what the part is called in the parts list.
But the little tab on the lever is clearly designed to be easily pressed; it might, for practical purposes, be called a release... One could argue that if they didn't mean for it to be used to UNLOCK (i.e. RELEASE) the slide, they wouldn't have put it there -- nor would they later have designed an EXTENDED version (on the 34 and 35, compatible with other models) to make it even easier to do so.
That extended tab isn't needed to LOCK the slide back more thoroughly -- only to release the slide more easily.