The P-8 is indubitably equipped for boom refuelling, down to a matt-painted panel above the windshield to keep the sun out of the operator's eyes.
Exactly why, I don't know. The kit had been developed and paid for under Wedgetail and it may have been considered valuable for certain missions and heavy/high-drag configurations (such as carrying a
ing big radar around).
I suspect that the P8 will not routinely use the AAR capability while operating in the maritime environment, however in an overland operation such as Iraq/Syria, where boom tankers routinely inhabit the airspace, then AAR would be an option. It is far better to have the capability and not use it, than to need the capability and not have it.
AAR on Wedgetail has already proved itself a very useful capability, though it does make for extremely long flights. The P8 carries more fuel than Wedgetail, about another 7 tonnes, so a single refuelling will push P8 mission times out to 20+ hours; good luck with that!
Y_G