Johnston wrote " I just wonder what happens when an HIV expert starts talking to a cancer expert about what LL can do, if the cancer guy might think the HIV guy is out of his wheelhouse".

Nope. When these super specialists get together the thing they discuss is the mechanism or mode of action and how they see that drug working in their specialty. These specialists want to advance the care in their particular specialty so the more diverse views and actions they can appreciate, the better chance they have of coming up with a better treatment modality. These people see connections where most people just see a blank screen with unrelated bits of information.
Sure, there exists competition and maybe jealousy but they all understand that is what makes the game even better and the patients wind up with the benefit.
Who will be regarded as a modern day Alexander Fleming when that person puts it all together?
Stay tuned in. I believe we are on the correct channel here.