Yup. And this is the context in which Raven's claims make more sense.
Evidently his first self-printed and locally-distributed with his friends (like your first RPG from the 70s) was around 1980. This new "3rd edition" he's just put out is the ninth version he's put in print, by his account. I've personally owned four. Wiki accounts for the 1991 (Dameon Willich cover) and 1993 (Posada brothers cover) versions, and mentions the 2012 Kickstarter for a reboot, but I bought an earlier edition which he was printing and selling locally (and, it appears, by mail with ads in Dragon Magazine) in either 1990 or early '91, before the DW cover edition came out. I don't know if the versions from the 80s were as complete a game as that one, or if they were more patchwork kit like Arduin. But based on my experience with the system, I'd lean more toward the former.
Oh, I entirely believe that he was publishing stuff, for some possibly loose definition of publish, going all the way back to the early '80s or honestly even earlier. It would be utterly plausible. 100's of people did that in bigger and smaller ways. AG was one of the more prominent, but I've heard tell of some incredible GMs, some guy in Atlanta, another in Chicago who had some sort of 'matrix like' campaign that actually freaked out the players so much it finally imploded because it was spilling over into RL! Mostly they just photocopied stuff for people that played with them, or asked them for material.
So Raven's claims, while hyperbolic and maybe a bit self-deluded, aren't as crazy as they seem at first glance and wiki check.
I mean, I don't think his basic assertion that he was publishing a game is nonsense at all. I think assertions that there was any sort of activity against him, or anything like that, or that someone genuinely conspired against him is a bit different though. I'm open-minded, evidence would convince me. Tall tales are merely that however and probably remain forever within the realm of unverifiable story.
Not to say that cross genre didn't already exist prior to that, but (and I haven't seen it personally to confirm) if his first version had anything like the later editions' mix of fantasy, sci-fi, and superheroes all together all at once back in 1980, then he really did something different than earlier publications like Arduin, Tekumel, or Superhero: 2044, and he did precede Rifts by 10 years or so.
Eh, I just don't think strict genre adherence was so much of a thing back in the early days of RPGs. MA/GW was CLEARLY just someone hacking on D&D to make a campaign with Sci-Fi stuff in it, for example. Clearly those games WERE mixed with D&D, as Expedition to the Barrier Peaks amply demonstrates. I'm not sure you can discount EPT so easily either, it really IS a cross-genre game! A lot of people may have played up the fantasy side of Tekumel, but it has plenty of both! Also, while RIFTS itself dates from about the same period as the actually released 'pro' version of Ryan's game, Kevin was putting out a stream of crazy stuff at Palladium going all the way back to the early days, and it all pretty much tied together into a somewhat mushy 'system'. I admit, pre-RIFTS he didn't publish an 'everything in a blender' explicitly, but I've always seen RIFTS as him just making totally explicit what was ALWAYS a fundamental aspect of his work, that it all was just craziness and you could mush it all together, and were encouraged to do so.
So I find Ryan's assertions that he pioneered this kind of play and that his system is its first manifestation a bit much. Basically c. 1979 if you went to a game con and threw a 20 sided die in some random direction, it was likely to hit a GM who was doing something extremely similar. Albeit maybe they didn't ever publish a book, but it was really a pretty common trope, the 'kitchen sink RPG', almost invariably based on some flavor of D&D, though sometimes perhaps owing more to Champions or something like that.
In fact we, in '78-'79 playtested some stuff that was written up by guys that were in Steve Jackson's 'crew'. They would come up to The Bunker, where we had around 200 active gamers, and hand around copies of their TFT (or at least proto-TFT) based stuff. There was 'T.H.E Fighter', 'T.H.E. Mage', etc. and there was a bunch of cross-genre stuff in there. I guess it didn't lead anywhere maybe, or it all got mushed into what eventually became GURPS, I'm not sure. I don't think Steve himself was directly involved, or at least he never made the trip up to see us. That was still back when Metagaming was a thing, so it may have all been a bit wrapped up in that.
In any case, I would agree that really explicit "all genres are here" wasn't a mainstream RPG supported kind of thing, explicitly, before about 1990, but it existed. My feeling was always that stuff like that was pretty much how people played, and the published genre-specific RPGs were sort of just the raw material. That was one reason why universal systems like GURPS and URP (SPI's attempt) were seen as desirable, because they made the mashups a LOT easier!