I have done sous vide confit several time and love it. There are a few things IMHO that are leading to the confusion 1) size of the duck legs 2) amount of salt in the cure 3) how salty people like their confit.
Larger legs = longer cure time
More salt = shorter cure
Saltier taste = longer cure
I find Keller’s method (easy to find online) results in too salty a confit for my taste. He uses a lot of salt. I prefer the amount used in “modernist cuisine” (found another’s blog post about it here)
It takes a little give and take to get your preferences tuned in (more a factor of the cure not the sous vide method). I think the modernist method doesn’t use bay leaves which I think are essential …
