Yeah,..... Na. That's an American method, not for us down here.
The ropes running to the boat are not legal in most of NZ (too small), even if they do employ a technique I myself use and did say big steel a few years back, the un-equal length theory.
Why connect under the buoy in place you can't easily see it - DO NOT SIT THERE THINKING 'BUT I WILL CHECK IT', No you won't, best intentions are good but it'll quickly be forgotten - that is also a wear zone and with critters trying to make it home.
Why not put the connection on top of the buoy and run 2 lines from there to your boat, 2 lines that are legal and in the 'BFO' size zone, cleaner, safer, cheaper, smarter
PM coming at ya.
BFO = Big F**K Off