Allow me to add to that... Base GCD is 2.50, as we all know.

Greased Lightning I = 5% = Monk-exclusive base GCD is 2.40
Greased Lightning II = 10% = Monk-exclusive base GCD is 2.25
Greased Lightning III = 15% = Monk-exclusive base GCD is 2.12
Greased Lightning IV = 20% = monk-exclusive base GCD is 2.00

As such, the Greased Lightning traits are for certain still there, there is no doubt about that...

Yoshi-P's GCD in that Live Stream being 1.97 just means that he had almost +0 Skill Speed.