Yup, those are the 3 standards I see. The FL, FR, RL, RR is rather simple and I suppose what one would expect. The FL, RL, FR, RR made sense for consumer quad reels, because that would make the front stereo pair line up with the stereo pair of a stereo tape, making it easy for a reel deck to do both stereo and quad playback. And then there's the RL, FL, FR, RR layout, which was rather common among electronic composers, and also has a mindset of thinking of the layout as a wide stereo field.
You know, I'm now remembering a seminar on surround sound I attended in college, so this would have been late 90s, early 2000s, and at some point the topic of track order on master tapes for 5.1 came up, and there were a few different standards there. And I recall an explanation that was given on one of the standards was to put the center channel early in the line up, because sometimes TV stations were getting masters, and would just pick the first 2 tracks to use since they were only broadcasting in stereo, which in one of the standards was laid out to start with L/R, and as a result there would be no dialog, or very quiet dialog, so changing the order to L/C/R..., if you got a TV station that did that, you'd at least get dialog, and half of the stereo front. Not sure if I remember that all correctly, or how often something like that happened, but something I remember hearing anyways.