Well, I just ran the experiment, looking at bokeh (I don't disagree with your point about exposure times--thank you for the clear explanation, too, it was one more bit of technical education for me). There is a noticeable difference with the lens at f/1.8 focusing on near clutter with a painting about 20 feet beyond, bokehed out, versus same lens, same camera (an M50) at f/2.0. A face on the painting that's about a foot tall still has darker areas for eyes and mouth at 2.0, and loses about half that on its way to being a uniform pink blur at 1.8. (Hypothetically, 1.6 or maybe 1.4 would reduce it entirely to a pink blur.)
But it's not a gigantic deal-breaker difference, except maybe to a bokeh fanatic. Still, I'd pay a bit extra for it if I had the option to.
And I'm glad to see signs of RF lenses for mere mortals being developed. It shows, I think, that Canon really does want "regular people" (well, regular people who prize full frame, admittedly that's already a pretty select group) to move there and it's not going to remain a boutique (albeit backward compatible) mount any more within the realm of full frame.