Yes, it is a safety. It is a physical block, that unless it is actuated, or there is a malfunction, the gun will not fire.
It's not a very good safety, but it's a safety. Just like the safety on a Bic lighter.
Buy a new spring and check it's strength vs. the old one every 1k rounds. When you notice a difference when racking the slide, keep the new one in there.
The granulate grips are not similar to skateboard grip tape. They ARE skateboard grip tape, cut to fit your firearm of choice. The reason I know this is because I skateboard and I watched a few installs of the grips on YouTube, and they use MOB and Jessup grip tape.
Since the grips wear out...
I would not want a holster to break in like a baseball glove. A broken in baseball glove is floppy, and doesn't hold it's shape. The last thing you'd want in a holster.
I'd rather have leather wear on the slide than a bullet in my *** because the holster folded over.