Same respsonse for me today from the HGP representative here on FT:
"I show that a DSU wouldn't be available during that time. I know the suit they use is showing available. There is somewhat different availability when using P+ C and a DSU. The hotel is showing that P+C and P+C+ DSU is sold out at this time so I would be unable to process the DSU. "
This is the PH Tokyo. I have a c & p reservation, several entry suites are available, but they wont let me use a DSU. I may try the Twitter team instead.