If I’m reading this correctly it sounds like it might a kind of beneficial graft-vs-host reaction?

The HIV-free transplanted immune system sees the original immune system as alien, and proceeds to wipe it out at the cellular level. This presumably takes the HIV with it, even if the new immune system is not itself resistant.

I guess this means that quiescent HIV is not at a stage in its lifecycle where it can reinfect cells if its host cell is destroyed. My hilarious mental model of infectious HIV virions floating inside a CD4+ T-cell like angry bees inside a balloon is clearly mistaken.