It sure does.
For your usage...absolutely. Very nice post. Logical. Reasonable. Fun to read. Even educational!
For my usage?
Not so much.
My statement from earlier:
"This is one of the real world comments, at least for me. Well done."
Of course it may not work for everyone, everytime, but the same applies do IS. If, out of 20 people, one complains that IBIS didn't work for him, the system was still successful for 95% of the users.
Canon often develops the fastest lenses without IS, they did the same on EF mount. EF 24, 35, 50, 85, 135...all the fastest variants were unstabilised, and the same happened with a few zooms, like the 24-70 f/2.8 and 16-35mm f/2.8.
It is my understanding that including IS requires the lens to be able to cover a larger image circle at least at some point of its construction. When designing for the extremes, that may certainly be an issue.
I'm shooting with R5 Mark II. Just sharing my experience.
Thanks for the graph, it was showing exactly what I think but the focal length is really missing. My absolutely subjective guess/feeling is that around 40-50mm it starts to count. In average situations that is. There are always exceptions like you are in an Italian village at night, near the sea, interesting clouds lit by the Moon and you are trying to shoot 1/4s at 28mm handheld to make the waves silky. Or whatever

Point is, I has a few occasions where are really appreciated IS at wide angles and managed to get shots which were impossible 10-15-20y ago.
IBIS does pretty much the same. At those focal lengths it may be even more effective than IS alone.
For a moment there you made me think twice, and I had to grab my R6.
The 45mm was attached and I managed to get sharp corners at 1/4 with ease, and about 50% keepers at 1/2.
I didn't bother dropping further, but I think that's about 4 stops of IBIS on a lens that is CIPA-rated to go up to 8 stops. IS lenses usually don't go beyond the rating of 5 stops (CIPA) on their own, with many users barely getting 3.
Usually I can get better results with the 28-70, thanks (I think) to its weight.
With the 16mm I know I can go something over a second of exposure, but I don't remember if I can get to 2 seconds, I suppose not.
The higher resolution of your camera may make it harder, but that difficulty increases for IS as well.