It seems to me that they have an old sward of poa and with the amount of play PB gets, even if they had a frequent program of greens turf stripping, and replanting a bent cultivar, the poa would be back by the time the rootsystem matured enough to not have all sorts of other agronomic problems - say a three to five year stand maturing of greens turf.
So, what do you think it will be like at Chambers Bay in 5 years? That greens turf sward has reportedly had trouble establishing itself. By the time they get the US OPen, I'd have to bet that the greens there will be mottled with a high percent of poa. And, what purity will that fescue in FWs or surrounds of greens have by then?
I don't know about Donnie's comment that light watering and/or syringing would keep the poa plant healthy enough not to collapse on the plant cellular structure and prevent the phenomenon of pitting or unevenness, and how that plays into the rapid amount of growth the plants reportedly do in one day out there in that climate.
But, I don't think that the collaboration of the USGA guys set-up wizards and the turf staff is one of ignorance. I'm sure they know all the things that get suggested here. But, they have their ways...