i mean well as far as speed is concerned, some editors need intermediate codecs to work smoothly and thats understandable.

but how can you increase quality just by upsampling?that i dont get.

if the workflow was to open an 8bit 4:2:0 video and denoise, deartifact and then add just a small amount of fine monochrome noise and then save as 10bit 4:2:2 then it would make sense(even though you dont have to do that and then reopen the file to edit it, you can do all this at the same time and just do a final export)

or maybe its a final cut/apple mac thing that i dont understand.
maybe in final cut when you open a 4:2:0 8bit file your project and everything you do in it is being calculated in 4:2:0 8bit and being kept there.
like trying to assemble and ikea chair inside the box you purchased it : P

i just dont get it.