Closing the loop, I think I now have the answer:
If you’re running a stock BBL printer with a 0.6mm nozzle, then, no, high speed filament just isn’t going to matter, because your speeds will already be considerably slower than they were with a 0.4mm nozzle.
The proof is here:
What about if you’re using the 0.4mm nozzle, or using an upgrade like the Obxidian? I don’t know. Maybe? I can only guess, because I’m saddled with this 0.6mm stock nozzle for now, and will be until I finish an important print using PET-CF, which is my whole reason for shifting to 0.6mm in the first place.
What strikes me most is most people don’t seem all that interested in the question, let alone the answer. Meh. Maybe the crowd is right.