It does make sense that they'd test features on low end products, but I'm not sure it aligns with where they make their money. I had always understood that Canon makes most of their money on those low(er) end models so taking risks there wouldn't be a good idea. I suspect they're pretty sure a new feature will be functional even when it gets into a low end model, though maybe the experience with a lower end model results in fine tuning in higher end models. I've always felt that Canon's value proposition was centred on high-quality lenses and rock solid reliability, and I don't remember the last time they released something that didn't work as intended.Keep in mind though that we already know of a Full Frame Mirrorless camera that was registered a while back and only has acerage resolution:
K433 // Canon EOS Rx
Wi-Fi · Bluetooth
Quoted from https://www.canonrumors.com/breaking-down-the-latest-canon-gear-to-appear-for-certification/
In that rumor it was mentioned that CR guy thought there would be no camera below the R. But that obviously changed over the more recent posts.
Isn't Canon usually doing this tickle up game, where they test their core features on lower prices bodys and release proffessional one later? Dual Pixel AF (70D), Swivel Screens (T3i), Touchscreens (T4i), their entire mirrorless tech (M6, M5 M50...), all that is quoted as being good about the R comes from development of lower end bodies. Maybe they want to continue with that for a while until they can really justify putting it all in a true 5D or 1D type camera.
With that said, a low end R lines up perfectly with where Canon makes money. If they sell a lot more cheap cameras than expensive ones, then I'll bet the rumours are true and a cheap R is next. If it's cheap, it'll sell well.