I want to add that instead of subtracting one category from another, you can also copy and paste the GWP-total to create a new category and rename it to GWP-GHG. Then you go inside the characterization factors table and you remove (or you set to zero) the biogenic carbon dioxide flows like "Carbon dioxide, non-fossil, the "Carbon dioxide, non-fossil, resource correction" if it exists, and the carbon uptake flows like "Carbon dioxide, in air". This would give you the GWP-GHG from PCR 2019:14 compared to the GWP-total from EN15804+A2.
Surprisingly the PCR 2019:14 does not change "methane, non-fossil" back to "27.0", so the characterization factor for biogenic methane stays as it is in EN15804+A2. If there would be the biogenic correction for methane, too, the GWP-GHG would be simply the same as GWP-total in EF 3.1 (not the EN15804 version).