Anderson may well have squatted what he claims, MANY powerlifters hit their all time PR's in the gym and NOT on the platform due to various reasons (General nervousness, choking in front of crowds, self conscious -not fully focused, weight cutting, social anxiety, etc.) , the issue (in my mind at least) is more the quality, would his squat have passed in competition? Without photographic evidence we can't know, that's why competition results are the standard.
The unspoken other side of the coin is, what could / did someone like Lee Moran squat in the gym? Ed Coan is full of stories of higher gym lifts than comp lifts that he's done and witnessed. Paul Anderson has a legitimate place as a pioneer in iron history but between his unsubstantiated and patently false claims (Pics clearly reveal poundages lighter than that claimed in some) it's apparent that he had a remarkable gift for self promotion that rivaled his lifting talents.