I'm not sure what you're saying -- are you saying that I inaccurately stated the experimental results of the study, or are you disputing their clinical relevance? I didn't really make any claims about the clinical relevance of this antibody study, but I do think that it suggests that the current CDC guidance (of recommending 2 doses even for those previously infected) might be overkill and that it would be worth further study of whether 1 dose (or even 0 doses) would be sufficient (including against variants) for those previously infected.

I don't know of any study of the Delta variant (or other recent variants) comparing immunity acquired from infection versus immunity conferred by vaccination -- AFAIK, it's still unknown how these compare and whether a vaccination might provide additional immunity against variants. IIRC, the mRNA vaccines were developed to target key parts of the virus that are thought to be unlikely to mutate without decreasing virus viability.