On the SX700 / 900 the rotary change is immediate when achieved using sample switching, and accelerates / deccelerates if achieved using DSP.

And those sysex data streams....

F0 43 10 4C : XG parameter incoming (page 122)

03 : Address HH
01 : Address MM
02 : Address LL
01 : value
F7 : end of Sysex

Address 03 - insertion effect parameter change (page 101)
01 - insertion effect number - 1
02_- insertion effect parameter number 1

So, the rotary effect used must be Real Rotary as that's the one (that I missed earlier) where parameter 1 switches the speed!