Sony and Olympus are the worst of these because they don't trickle down features and capabilities to their other lineups unless you buy a new camera ... Sort of, even flagship cameras are missing features that newer camera do have.
For Sony the High Resolution is locked behind the a7R series and a1, the Birds Eye Tracking is unavailable to a9, a9 II and a1 which is their wildlife cameras but A7 IV has it, Focus Bracketing is available only for a7R V and a6700 ... And if you want one of each of these features (which I do) you need to own at least 3 cameras (for a total of over 10.000 £) and that's something fixable with a firmware update.
Not sure this is at all accurate. It may be a viewpoint, but let's dissect it some:
even flagship cameras are missing features that newer camera do have.
In some cases they have no choice. The A1 was updated to the latest AF
including Bird Eye, after the A7 IV was released, but in the case of the new 'AI' focus in the A7R V, it requires an entire second chip. Not something that can be updated with firmware. I'm certain the A1ii will have all of that.
Most don't think of high resolution as being 'locked behind' the A7R series and A1, most think of the 'R' series as simply a different offering. For example, I don't want that many MP, and am happy to be able to buy a camera that doesn't have it. And if cost is the issue, you can still get an A7R III with 42MP for around $2k. That's still pretty high resolution by anyone's standards. And, the A7RIII does pixel shift.
It's not true that 1/8,000 shutter is limited to the A9 and A1. The A7 IV has 1/8,000 shutter speed, as does the A7R III. It's actually available on all of their full frame cameras, not sure about APS-C. Uber fast burst rates are definitely limited to the A9 series and A1.
Again, bird eye focus is on the A1, including bird eye in video mode.
I dislike the fact that the majority of Sony's firmware releases are to fix issues, and that they rarely add anything. To be honest, Panasonic is about the only one. They added a ton of AF features to the G9 over a few years. Other than that, I don't recall anyone else going the extra yard.