FWIW I don’t think die size is specified in the datasheet. Scaru talks about some die sizes here though.
I wonder if the bond wire size is the same for the XB-H as the XP-G2?
Unfortunately I’m not seeing anything immediately useful to us here. Now if they were to cram that ~2x2mm XM-L2 die into the 3.45x3.45mm XP-series package… EDIT: oh nevermind, they are doing that now 