UK physical splits are still useful for extrapolation. We just gotta adjust and assume a stronger digital bias for Xbox ecosystem than previously thought, as a consequence of Series S dominating later months as opposed to PS5DE representing a small percentage of PS5's sold.
Initially, GfK's physical splits reports combined Xbox systems, but now they're often separating One from Series XS, giving us a slightly clearer picture of what's happening. If I'm not mistaken, FW physical sales are typically PS5 >> PS4 > X1 > XS. This shows that digital bias for Xbox is directly tied to Series S's dominance.
In 2020, it was reasonable to assume a fairly frequent 5-10% change in Xbox's favor when digital is accounted for. It's safe to now bump that up to 10%-15% for games that don't have digital discounts, and maybe 20%+ for games that do. The increased digital bias has less to do with Xbox community favoring digital, and more with the production volumes of digital-only consoles; a factor I initially didn't think much of because Series S had a weak early demand and I didn't factor in Series X production being anywhere near as bad as it turned out.
I expect 2021's overall digital sales on Playstation and Xbox to be much closer than last year's.