I've hit this over the past week browsing the web UI. For some reason, github sessions are set really short and you don't realise you're not logged in until you get the error message.
From my experience in the finance dept of a few large Australian apparel retailers, I see BNPL sales from online at around 35% of sales dollars and in the brick & mortar stores around 1-3% of sales dollars.
I really wish github would stop logging me out.