Heh, don't ask me. Keeping Chrome running is a proven fix for the stutters many people experience in some of the more buggy games (DX:HR Director's Cut being one).
Running your browser in the b/g doesn't hurt performance one bit, modern OS's can easily juggle multiple gigs of memory among multiple apps.
I have ~10 tabs open at any given time and never shut down my browser even while gaming. And I doubt I am the only one who does this, I believe this is pretty normal for most PC users nowadays.
Back on topic; low framerates and more importantly stuttering is a valid reason for RMA. It's a 1080ti and not some budget gpu.
Don't feed them any dubious claims like 'VRAM can't handle huge loads', just present your problem as it is, it's a genuine case.