>This same breakdown implies that vaccinating half of the currently unvaxxed would do a lot to reduce pressure on hospitals.

This ignores the demographic differences between the vaxxed and the unvaxxed. The elderly and those with conditions that made them high risk have a much higher vaccination rate as one would expect.

If you cut the number of vaccinated in half you won't cut hospitalizations in half because subgroups of the population being hospitalized are not present in the same ratios in the unvaxed.