Hi again.
For what it's worth, this is the switch PoE status page (at the time I took this, 3 of the R710's were connected to ports g2 - g4), with port g1 - g8 all theoretically able to deliver full PoE+ 802.3at power, and all connected APs are correctly identified as Class 4.
And here is an example LLDP port config for g2, showing optional TLVs transmission, which includes Extended Power via MDI.
Yet the R710s still stubbornly stay in 802.3af PoE Power Consumption Mode.