Now the suite is showing around that time at standard rate, and I was able to apply the SUA with very little pushback from the hotel. Also, did it for only 5 nights, not 6, it actually wasn't available for the extra 6th night I booked only so I could drop it.

The only issue was that my stay was split across a few consecutive reservations and the Hyatt rep said that would then require N SUAs, and the hotel wouldn't merge the reservations. I pointed the rep toward a booking I have at PH Kyoto in the same situation, and when they looked at how it was done with a single SUA (some sort of annotation) they called the hotel to confirm it was OK, and now I have the SUA showing on all the bookings.

I have no idea what prompted such a change in attitude from the hotel side compared to days ago. Too worried about the situation in parliament to play games with suite upgrades? Probably not

By the way, the spa rate is back for standard room, no award availability of course.