So we arrived at MNL an extra hour early this morning and spoke with the ticket agent. My coworker - who is a very seasoned, experienced global traveler - politely told the agent we booked several months in advance and cannot travel Econ. She asked the agent to confirm that our seats are truly Biz and also asked to see a seat map. They assured us they were Biz and printed our boarding passes - our changed PremEcon seats that were in rows 24 and 25 are now showing us in row 4. Crisis averted!

Additional observation: the Mahubay lounge makes me long for the Star Alliance lounge in LAX.