The actual riffing style won't change, since Terrance is still there.
Like I said though, I've heard rumors that I'm inclined to believe based on what Mike has said publicly in the past, that suggest he was trying to push the band in a direction that appeals to a wider audience.
As you can see if you compare any of the post reunion material with everything up to Despise The Sun, it's definitely believable.
And I'm not strictly talking about the riffs themself, more the way that they're presented, along with Frank's gradual change to a more palatable vocal style.
Culross definitely gave them a different feel on Despise The Sun though, even on Catatonia (on which Mike wrote the drums)