Was there ever any additional follow-up to this?
I've had exactly the same problem as well since upgrading to 200.8. I only have a single R720 to test with (along with several H510s, which don't require 802.11at), but I have tested with multiple ports, multiple cables, and two separate Netgear MS510TXPP switches, all with the same result.
The switches autodetect class 4 (802.3at) PoE for all my Ruckus APs, so I can't find anything wrong on that end.
I'll also note that I doubt the workaround provided above is actually doing anything. Yes, if I manually override the PoE setting on the R720 to 802.3at, it will show "802.3at" on the status page, but I also still get the warning about power. I really can't imagine this option allows the AP to draw more power than it believes the switch can provide (which sounds like a great way to damage some hardware) vs. operating in a lower power mode than the current PoE source can support.