I think the general use expectation is one bottle per clutch type differential.
Isn’t supposed to matter what brand (Ford, Dana, GM…) or type of differential (as long as it’s a clutch limited-slip), you just use one bottle.
Having said that, I had a Ford Racing four-spider 9 inch track lock that required two bottles.
I was using Stay-Lube brand non-synthetic gear oil that was supposed to have the additive already in.
Still needed the friction modifier to keep it from growling.
Very possible that it was the clutch material and extra preload from the springs of the performance version, but I did give it a couple of months to soak into the clutches, just in case. And it still needed the additive.
Fast forward to the next oil change, and I used Redline synthetic, and it did not require any additive.
It was also so slippery that the differential did not transfer as much torque to the loose wheel as it did before with the regular oil.
Noticeably more slippage.