When I woke up this morning, I checked LotW and noted that I had received confirmation #100 in LotW for 160m from Ark 4O7CC (Montenegro). Just like that, my quest for 160 meter DXCC was complete. I received a nice note from Ark, after thanking him for being #100 – turns out he is a master on 160, with 325+ confirmed on that band, mostly from his home station in Russia UA4CC.
I filled in an application via LotW about 7:30 AM, and by 3 PM today, it had been completed. So things are official now.