I have done a search on this particular topic on the threads. There is absolutely not a consensus. People have reported speaking to various cast members and gotten various answers about whether any portion of the service charge is a tip. These responses have come from guest services, management at Palo, and individual servers at Palo.
I do think Disney could be clearer on this matter.
On the Palo home page, tipping is not mentioned at all, just the upcharge:
http://disneycruise.disney.go.com/ships-activities/ships/dream/dining/palo/#reservations
You have to go the onboard services page for info on tipping:
https://disneycruise.disney.go.com/planning-center/my-cruise-plans/faqs/onboard-services/gratuities/
For all others positions, the policy is clear. And, for port adventures it states specifically that gratuity is not included.
If none of the upcharge goes to the Palo (or Remy) servers then Disney should state that.