In this construct, West plays 5♦ opposite the three kings, rather than the 15% 6♦.
If East's diamond is the queen, 6NT is 100%.
With singleton honours, we downgrade kings from 2 to 1, and queens from 1 to 0.
We still show stiff kings by PCB. (not DCB with singletons)
Look like we should maybe do the same with stiff queens, so "don't count but show".
This might create some ambiguity. Is it worth it?
With the actual, we have another path.
4♦ over 3♥ would say "My next bid will be a natural slam try, requiring good trumps."
That would work here.