That was a little different. That was always meant to be PG-13, it wasn't cut to the rating after the fact. In fact I think the first two of those were actually the opposite situation - they were planned to be PG-13 films, but they R'ed them up in post with all the blood and dismemberment, which is why all of that stuff is conspicuously CGI. I definitely remember hearing that about the first, not so sure about the second.
But a ton of Stallone's 80s and 90s film were hacked to bits after filming to lower the rating. It often wasn't even subtly done - for instance, there's that really odd bit in Judge Dredd where the unfinished clones start waking up, one of them glares threateningly at Dredd and he racks his pump gun... and then it suddenly cuts to the place starting to explode, Dredd's chasing Rico around upstairs and the clones are never mentioned again. It was obvious set-up for a confrontation that then got excised lol. Demolition Man's terrible too - the old black cop simply disappears from the film because a scene where he was killed by Snipes at the end of the second act got taken out. Several of Snipes' henchmen also vanish, most obviously Predator's Jesse Ventura.
