I wish I had my OW book from 1995. I simply can't remember if there was anything in there about overhead environment. And, if overhead environment wasn't explained, I wouldn't have known what it meant, anyway.
but, my book is long gone, lost in the divorce vacuum. Oh, well.
Judging by what was in the 1988 version and the manuals used since 2005, I am sure it had rather strong language in the 1995 version. It would have explained that without additional training and equipment, that you have a good chance of dying if you go into a cave, cavern, wreck, etc, where there is no direct access straight up to the surface. Perhaps the instructor did not stress it enough but I am sure that manual was clear.