As a datapoint, had upgrades for 2 Plats on HEL-LPA-HEL clear at T-10 for outbound and again at T-10 for inbound. Both flights still have plenty of availability in business but had to go through waitlist.

For the inbound I checked right after midnight at T-10 and the flight was suddenly showing U4. Contacted the chat and had upgrades cleared right away. The flight went to U0 after that so I wonder if they cleared more people on the waitlist at the same time? And what if I didn't contact CS, could someone else have taken the 4 upgrades?

Also, interesting op-up situation on a recent MXP-HEL. My brother on an award ticket who is AY Gold got the nice beep at the gate. Myself as OWE and a friend as Plat who were part of a booking for 4 people didn't get an upgrade. From what I could see 2 other passengers got an upgrade as well. I would have wanted to use an upgrade voucher on this flight but U class wasn't available. Y was oversold at the end.