"What it really was was the introduction of the home VHS machine. "
Well, that came some time after Playboy. Actually, there was a brisk market in the 50s and 60s for 8mm stag movies. Since home movies were a popular thing at the time, many households had an 8mm projector.
There were a number of outlets for 8mm porn, and it was pretty popular among the young adult male set. You run across a stash of them now and then at estate sales these days. They're really, really cheap, as are the projectors.
The movies are rather crude, though, in comparison to the more heavily produced VHS porn tapes. Still...they were popular.
I'm just old enough to remember the pre-VCR days of porn, and while I don't disagree that those films were out there in large numbers back then, it's just nothing like what home video wrought. The home adult film biz in those days was small and underground. Most of the distribution channels were mob controlled--adult bookstores or PO boxes. Plus the films could only run, I think, 20 minutes tops in 8mm. The VCR caused a huge boom in the business. There's also a case to be made the porn is what showed the mainstream movie business that there was lots of money to be made selling home video directly to consumers rather than basing the business on rentals. Remember when a VHS movie cost a hundred bucks?