Does a weapon with multiple exclusive damage types always count as a weapon of each type, or does it vary based on the chosen mode? Ex. the duelist's Precise Strike ability allows her to add her class level to damage rolls "with a light or one-handed piercing weapon." Would she be able to use Precise Strike when using a dagger (P or S) to deal slashing damage?
The intent seems pretty clear--you get the benefits only if you're actually dealing the listed damage type--but this inquiry was sparked by a situation in PFS, so the RAW is what matters. I'm not out for a reductive argument wherein the definitions of common words are called into question, but the CRB does not provide a conclusive answer.
The rules do not say so you won't get an official rule for it, but if you need for the weapon to be piercing it is safe to say that when you use that ability you would need to do piercing damage.
If you need a PF ruling I would go to your VL or Mike Brock, if nobody can really agree.