"God and His Man"; Master/Maser

In the afterword to this story in The Best of Gene Wolfe, the author writes that when the story was first published, "the word maser was changed by the proofreader (I was told, at least, that it was by the proofreader) to master. Not all the time, only sometimes." In my mass market paperback edition of Endangered Species (Tor, 1989), the inconsistencies remain, though they seem to have been removed with this reprint. Why weren't they fixed when the story was reprinted the first time? I've never seen the Isaac Asimov's Science Fiction Magazine edition. I looked the archives of this list, and it seems that there was some discussion of the master/maser being a deliberate change. It's not too hard to invent a rationale for that.