Historic plaster to receive new plaster skimcoat

We are refurbishing a historic building that has many existing plaster walls. If a new plaster skimcoat is applied, do these existing walls still count for this credit? This question is similar to the ones posted here about refinishing wood floors and resealing existing concrete, but the new finish in this case is opaque- not just a sealer or a stain. Is there a way to draw the line here in terms of which refinishing treatments warrant credit and which ones do not? Almost 100% of the existing interior walls will remain, so it would be a shame not to be able to count all of that material.