That seems a bit...odd.
So basically I can do ↓ ↘ ↓ → +PPP and perform the ultra...even with a 360 pad?
With a pad it would be pretty hard, the d-pad is quite small for a start. It's mainly for those using a stick, when you switch on inputs in training mode you can see exactly what you are pressing and the above inputs you quoted are sufficient for ryu's ultra.