For a 6 month period you might give the same information to both sessions, so you do it twice (scan your face, passport, w/e). If Sumsub (or their competitors) used the info they︀ got from you 6 months ago, then what's to stop someone else from using that︁ same older info to create a brand new account under your identity?
So for that︂ reason, even tho you register for X platform now, and then register for Y platform︃ in 6 months, even if they both use Sumsub, Sumsub won't give platform Y info︄ it got from platform X.