I've got to believe this must be very safety dependent, and there are an awful lot of different 1911 thumb safety designs from the old GI style, to Colt teardrops, to the large modern "tactical" styles, and then the low mounts. I don't know how a holster maker could possibly take into account all the different options.
While I've never had a holster designed specifically to ensure the safety is engaged, I'm skeptical this can be accomplished, since my teardrop safety, regardless of the condition it is, merely pushes the sweat shield out of the way.