I mean think about it - it's something like, Sammy was cleared by the inept training staff (over which Rex had no control, not that he would've exercised it), was forced back onto the field too early and wasn't himself, then the new regime comes in and declines the option because of his injury history and his inability to play at a high level of late.
Wouldn't surprise me at all if that's how it went down, and in response, his agent made it clear to Beane that re-signing Sammy was gonna be near impossible.
The thread of ineptitude extends throughout human history and certainly modern Bills history. Everything repeats and everything is linked.