.
Canon's naming convention and corresponding model specifications have every bit as much to do with build quality and battery capacity than they have to do with resolution and frame rate.
When I see people on forums discuss and compare different models, they never seem to give the same weight and importance to build quality (ruggedness) and battery capacity that they give to other things like resolution, sensor quality, etc. . I think this is odd, because build quality is of such utmost importance, and is the main determining factor for many of us when we are making decisions about what camera model to buy.
Choderboy, I didn't see you discuss build quality at all when you were talking about Canon's naming conventions and the differences between the different models and model lines. . If you would include build quality and battery capacity as being just as important as resolution and frame rate, you would see that the models you say "stepped out of line" didn't really step out of line nearly as much as you may think.
.
I think what you are saying here has a lot of merit, there is certainly more than technical specs that must be taken into account.
I do think there have been some big steps by some of the bodies. I'm not sure I think the 5D3 represents that but that's the only 5 series I haven't owned so my experience with that is very limited. In my opinion the 5D4 was a huge step up from 5D/5D2 in almost all areas. In fact it's the first body I felt like I could use for action without too terribly much praying involved in getting a decent result. I think the R5 was another huge leap forward, but....
I think the fact that the R series is mirrorless has created another technical distinct that has served to somewhat blur the lines between the series. I think for example, that the R5 is the first time Cyberdyne (Jake) has used a 5 series as his primary body for shooting action. Certainly it is FAR more capable than previous bodies for this use case, and before the R3 it competed in a lot of respects with the 1 series DSLR series...and at a much higher resolution.
I skipped the R and the RP. I think these were stop gap bodies until they had the more traditional series bodies ready for release. I do think Canon misjudged the acceleration of the mirrorless body age and were behind. I also think they did some market testing here (as in the touch bar that we may not see again) We will see, but I don't think you will see either of these names continue in future releases.
We are starting to see a more clear picture of their naming conventions now, and it matches up rather well with the conventions they used for their DSLR product lines (albeit we didn't see a 3 series DSLR). 1,3,5,6,7 (where crop starts).
It's all speculation at this point, but I think the stars line up this way.





