My brother went through a couple cycles of GVT and he got a bit bigger. Didn't gain as much as you did but I wouldn't be surprised if the scale moved up around 8 pounds. As long as you get a pump with a heavy weight, you're gonna set the stage for growth.
I'm a stickler for form though and I cringe whenever he shows me his videos of PRs. The other day he shot himself doing 220 lbs on the back squat (With his training age, I'd have expected him to reach that long ago) and he couldn't even get histhigh to go parallel. The whole night he was trying to justify his form.