Are you referring to the study referenced in Inside Medicine. What Are You Seeing? [COVID-19 medical news] - #5662 by ucbalumnus ?
That study found that, in those with 3 Pfizer shots but no prior infection, Omicron infection increased antibody response against ancestral, Alpha, Beta, Gamma, Delta, and itself (though, interestingly, the increase was least for itself). But it also found that in those with 3 Pfizer shots and prior infection with the ancestral virus, Omicron infection did not significantly increase antibody response.
There were human trials on bivalent boosters for other variants (ancestral + Beta and ancestral + Omicron BA.1). However, the problem is that by the time full human trials complete, the variant in question has been displaced by another variant (much like flu strains for seasonal flu vaccines). If you are really concerned about wanting human trials on the exact variant of bivalent booster, you can go to Europe and get a bivalent booster with ancestral + Omicron BA.1 instead of ancestral + Omicron BA.5 in the US.