Does Leblanc ult only change "On-Landing" of her Q? (Instead of on cast)

I am finding a great many times that I will attempt:

W, Q, R, E

As an example (I understand it isn't her biggest combo)

But what will happen is:

[W]Dash>[Q]starts flying>[R]Dash again (wtf now I'm all mixed up)>[E]...

I am pretty decent at fast-cast combos (aka, Kassadin)

However, I find on LB ult, the change on her R is too slow for a quick-finger combo.

Is it because it only switches when landing her Q?