In a preciscion tuned 1911A1 target pistol it MIGHT hurt something.
But since 1911, every military watch stander armed with this pistol used the slide release to drop the slide on an empty chamber at the change of the guard.
Even the "Manual of Arms" for the 1911A1 calls for the slide release to be used to drop the slide after "Inspection Arms".
I would think that in that pistol's long history, there would have been an advisory notice if that had been a problem. If we had a nickle for every slide dropped on an empty 1911 chambers, we would all be millionaires. If it caused any damage, Colt would still be prosperous.
Metallurgy has come a long way since 1911.
My .45 ACP Colts, USP, Sig and P9S have no caveats on dropping the slide on an empty chamber in the instruction manuals.
The unusual and dangerous ritual of pulling the 1911 trigger to unload the sear while releasing the slide is another strange custom waiting for an AD and a DA soon afterwards.