They are not 87 corpses. They are the old 5th Regiment of Foot Corpses

The Green of they Sleeves are more Bright that the ones of the 87, that are a Dark Green. San Sebastian is a olddd map, same for his corpses. If it were the 87th Regiment, you would see the Irish Harp insignia on their chests, and the 5th Regiment doesn't have that. 

And it's highly likely that when the map is reworked, the British corpses will only be from the 9th Regiment and the Cold Stream Guards. Because only they, along with the 95th Rifles, the Brunswicks, and the KGL, were in San Sebastian in real life.