I haven't seen the failure to update on my end, but there's a comment on the YouTube video where someone else says that's something he's seen. The OOG overlay should update.
Yes, that was me.
And as I said in that comment, I think the degree that the rendering intent will handle things depends on the image. I'm including the following in case it might be useful for yalag. I know that you already know all this, Andrew.
First, as you have said many times the clipping overlays don't tell you how far out of gamut the colors are so that can be a big deal. If the colors are only slightly out of gamut the small adjustment made, even with relative colorimetric, will be nearly invisible.
Second, even if the colors are significantly out of gamut it may not be that noticeable if those clipped colors are providing little in the way of detail information or if the detail provided by those clipped colors is very small. There will be some degree of hue shift but there will be little or no noticeable loss of detail.
On the other hand, if the clipped colors ARE providing detail information (variation in tones over the clipped areas), then relying solely on the rendering intent can be problematic. You can often see this in images of brightly colored flowers, where the colors are significantly out of gamut and those clipped colors cause a very noticeable loss of detail in the image.
For Lightroom users, I have found two ways that often help with OOG situations beyond just using the HSL sliders. One is easy; one is a little harder.
The easy way is to just use the Tone Curve while in soft-proof mode and pull down on the white point. This won't necessarily bring all colors into gamut but it will often resolve a large percentage of the OOG colors in photos of flowers and such - particularly when going to something like sRGB. It darkens the image some obviously but for on-line viewing in sRGB I find that it often works pretty well. The eye adapts to the lower brightness pretty well and you don't get the faded color that HSL adjustments will sometimes give you. It also seems to work better than the Exposure, Highlights, and Whites controls where LR tries to be smarter than you want it to be in this case.
The more difficult method is to use Adobe's DNG profile editor to make adjustments to heavily saturated colors in a custom camera profile. I still don't have one "perfect" but I have done some experiments and they work pretty good for non-commercial work. I think of it as a way to create my own "perceptual" rendering intent and by doing it with a custom camera profile, it works even for a v2 sRGB target.