The radioisotope is meaningless without the right molecule/...

The radioisotope is meaningless without the right molecule/ vessel. If the radiopharmaceutical is not taken and retained by the tumour, it won’t be able to kill it, no matter the amount and type of radiation used. On the other hand, if it is not cleared rapidly from the body, it can produce intolerable toxicity.
In this case, they are (deliberately?) comparing apples and oranges, as you cannot extrapolate (at all) that the dosimetry results attained in that study would have a similar outcome using radiopharm’s prostate antibody labelled with terbium. In fact, you can have a look at telix’s prostate compound, which is also an antibody, and has a very different biodistribution (and consequently dosimetry profile) when compared to pluvicto, despite having the same target (PSMA). In other words, it’s not clear that a terbium labelled antibody would have a more favorable dosimetry profile than a lutetium labelled antibody, that would depend on the biodistribution for those particular compounds.