Presumably with ultra minimal bezels there would also be rounded display corners (at least at the top) so this taller bar would allow those to not clip into any application, which could be on a perfectly rectangular section of screen below. That could explain making this bar taller than the current menu bar.No, it would be exact opposite of what you claim. A full screen would be same 16:10 screen ratio as before, but the permanent menu bar would be in the extra vertical 74 pixels above that, and that is where the notch would be located.
The problem with that theory though, as I've mentioned before and as @virulent says above, is that 74 pixels is about 7.3 mm, which is too tall for a traditional macOS menu bar.