I've had/seen this happen with certain combinations of 1911 and holsters, including a duty holster or two. I don't like big safeties anyhow so my 1911's invariably have the GI or Colt commercial style safety. I won't tolerate a mushy safety or one that takes undue effort to switch either direction.
These days I IWB with a Safariland 27 and I've never had the safety come off, even after long days.
I'm inclined to think if a man hasn't gotten his point across in 4912 attempts, 4913 probably isn't going to do it.