I'd be surprised if that didn't factor into the equation, although even just regular referrals would be acceptable for many uses where you can do some degree of load-balancing / fail-over with reasonable recovery times.
Not necessarily. IIRC, pNFS is an optional feature of NFSv4.1, so they might not have implemented that flavor. If they had, I'm pretty sure they'd be advertising it. They're not shy.
Technical details aren't out yet. They may not have implemented it, but given their comments about performance and scaling, it would be a very good reason not to support NFSv3.