I think you are missing the point that
@Czardoom is making. Individual consumers don't decide of course, but collectively all consumers decide through their buying decisions in the market. The number of camera models available is driven by the number of consumers who are willing to buy each model and what they are willing to pay. Consumers decide, because if the company cannot produce a specific model at a price that it can be sold at in the market it won't be made. Conversely, if there is sufficient demand for a product to produce a profit it likely will be made.
Canon
is rationalizing why they are making two different 70-200 f2.8 lenses -- they are rationalizing it by selling sufficient quantities to turn a profit. (Actually, I believe they make three 70-200 f2.8 lenses -- one EF mount without IS, one with IS and one RF mount lens).
It's a little silly to ask if anyone has ever seen a camera manufacturer with two separate full frame lens lineups. What other manufacturers have or haven't done is irrelevant to Canon. Canon now has two different full-frame lines. As long as they have two lines, they will have lenses to fit both lines. How long will they have two lines? As long as the market dictates. So,
@Czardoom's point is correct -- consumers will decide.
I'm beginning to feel as though you have some unstated, vested interest in a specific outcome. I'm just perplexed by people who have bought into the R system and now feel they must convince everyone else to follow suit. I own the R. I use the R. I like the R. But, it's not for everyone. Why do you care?