Glock sells their "extended" slide release, that comes standard on the Modles 34 and 35, separately. The added button is angled to make it easier to push down... not up, so it would seem they endorse the use of it as a slide release.
I've been shooting a 34 in IDPA and GSSF, as well as weekly practice for several years and the slide notch is just fine. No physical wear except for the black coating being gone. Perhaps I just don't shoot enough, but I suspect the slide is a bit harder than the slide release in any case.
Good luck.