When I fly around the Philippines, I never seem to be able to book a fare with miles accrual, but then I never look for full Y. As for switching seats, I've always been able to get what I want at the airport, but what is the point of advance seat selection then? Even the big US airlines that block seats for their Elite members never take 8/12 seats in their First or Business class cabins.
I don't mind PAL in the air, but some of their policies leave a lot to be desired. On the plus side, I just received a ticket refund from PAL 3 months after I'd given up!!!