I noticed, too, the T-rex seems to eat an awful lot! But then, the game wouldn't be as exciting or intense if the rex was just shown lazily napping for the whole game after one meal. The science reasoning side of me can justify it by pointing out that a warm-blooded metabolism comes at the cost of constantly having to eat, and as the timeline of the game spans a few days, one big meal per day plus one or two smaller opportunistic meals per day seems reasonable for a large tyrannosaur.
Plus, all the eating could be all the years of suppressed hunting instinct surfacing after a lifetime of being fed tethered goats.
(or maybe there was more than one T. rex...)