Earthquake stun

Sorry for my bad english,im not a native speaker.

Today I was in a NW 13 Key, and had a discussion with an Elemental Shaman about the knockdown/stun of Earthquake.
He said “Earthquake-Proccs dont stun if i use when its lighten up” ,
and linked me the Talent Mountains will Fall.
He said “I will get Proccs all the time so it will never stun when i press it,better i use (singletarget) Earthshock on this add”

Im not exactly shure what he means, because i didnt play Ele a year, and it got a massive overhaul ,mastery change ,talent change , last patch.

Last time i did play Elemental Shaman the Talent Mount will Fall deactivated the Stun only from the overloaded Earthquakes.
I didnt want it do discuss further with this Player cause i wasnt shure myself if it got changed since last time i played.

Did something change?
Something with base Earthquake,Overloads,“Procced Earthquakes”(whatever this is),or Mountains will Fall?

Context was the Trash packs between boss 1 and 2 in NW ,where the Caster summons little Skeleton minions.