i think that sums it up. Abbey Road may have been prog-like (and the general consensus seems to be it is) but that's a long way from calling it the origins of prog rock. Like Nyfan says, new genres generally stem from many influences.
The Beatles influence on prog is like their influence on heavy metal. The Beatles weren't exactly a small-time band no one had heard of. Take a song like “Helter Skelter” brutal arrangement and sound. Saying it is inventing metal, that's a bit much. I think that it influenced the people who invented metal. Both Ozzy Osbourne and Lemmy Kilmister cite the Beatles as their favorite band of all time, and the reason they originally got into playing music. Between Black Sabbath and Motorhead, we have the entire genre of heavy metal pretty much at the trunk.
As for music, the Beatles touched on so many styles that it’s more like they shot off tangents song by song. Think about “Hard Day’s Night” jangle pop/folk rock , Beatles For Sale country rock, “Hide Your Love Away” contributing to the emergence of singer/songwriter, “Drive My Car” and power/pop, “Day Tripper” and hard rock, Tomorrow Never Knows” and psychedelic/modern electronic music, Sgt Pepper and concept albums, and on and on and on..
They were in the vanguard, and the mainstream followed them. Most of those groups you say you don't hear a Beatles influence on would tell you just how much they were influenced by the Beatles. Read these remarks by two members of King Crimson and then you will get what I am saying.
What sparked that original creative spark that
became prog rock?
The Beatles. They broke down every barrier that ever existed. Suddenly you could do anything after The Beatles. You could write your own music, make it ninety yards long, put it in 7/4, whatever you wanted.
Robert Fripp on Sgt Pepper
Robert Fripp- "When I was 20, I worked at a hotel in a dance orchestra, playing weddings, bar-mitzvahs, dancing, cabaret. I drove home and I was also at college at the time. Then I put on the radio (Radio Luxemburg) and I heard this music. It was terrifying. I had no idea what it was. Then it kept going. Then there was this enormous whine note of strings. Then there was this colossal piano chord. I discovered later that I'd come in half-way through Sgt. Pepper, played continuously. My life was never the same again".
Brian Wilson of the Beach Boys
"Upon first hearing Rubber Soul in December of 1965, Brian Wilson said, “I really wasn’t quite ready for the unity. It felt like it all belonged together. Rubber Soul was a collection of songs…that somehow went together like no album ever made before".
Pete Townshend of the Who
"In a 1967 interview Pete Townshend of the Who commented "I think "Eleanor Rigby" was a very important musical move forward. It certainly inspired me to write and listen to things in that vein