I agree to an extent, spanner showed that point in time global snapshots can be practical. But many (most?) applications are fine with just serializable transac

I agree to an extent, spanner showed that point in time global snapshots can be practical. But many (most?) applications are fine with just serializable transactions, they don't need the additional real-time preserving guarantee of strict serializability. So I expect to see more of this in the future where constraints are relaxed just slightly.