I guess because I come from a triple background, I wonder how real life cross chaining is and how it affects chain life. I realize a double must put less chain angle than a triple, but I do wonder if chain life is a lot less than with older systems and triples where the chain is simply going to be a lot straighter most of the time. I guess we could also touch on the whole chain life/strength thing, ie are 10 and especially 11 speed not as strong as 8 or 9.
Di2 with 8050 (and presumably GRX) will not allow the two smallest rear sprockets to be used when the front is in the small chainring.
My guess is that Shimano shares some of your concerns. I also think they realize that some will push the boundaries of what's possible and are trying to put up guardrails.
Anyway, it is blocked in software. When I upgraded from 6870 to 8050 shadow/clutch, those two gears were simply gone.
-Tim-