Another one, without a clear victor.
I think the foliage and shadows have to do with the legacy code going all the way back to the base X1 and PS4. It very well could be that the X1 needed those compromises and the base PS4 did not, as we all know the power difference there.
Because those same differences are identical to the X1X and XSX/S, it could be the differences are due to these upgrades being texture packs and tweeking stacked on top of what is already there. And since the PS5 would be scaling up with enhancements stacked onto the PS4 version, the difference with small details like that remained. If it is true that the least common denominator for each console is being used and scaled up from their respective brand, it could explain a lot when it comes to these minor visual differences. This is not even a cross gen game afterall, but a gen 8 game enhanced.
I imagine this to be the case with cross gen games as well where these minor differences may be present. Seeing how in most cases cross gen is made for the least commom denominator, it is possible that the X1 could hold the XSX back more so than the PS5 if the developer takes the easy way out.
It will be very interesting to see how games made specifically for gen 9 turn out in the future.