When you get down to the last roster spots, guys who wouldn't make the game day roster which is where Begelton would likely start out if he makes it, it isn't just how many WRs they'll keep and who are the best.
Does Ervin show enough to be a psudo #4 or #5, a guy who might get few or no snaps in one game and then several in another to exploit a perceived defensive weakness? Do the TEs have their collective sh*t together to the extent that one is perceived to be an effective in-line blocker and another effective out of the slot, and occasionally wide as we've seen with Tonyan in the past?
Deguara was obviously drafted to take over the H-back/FB role right away. If he's not up to the task by a week from now a guy like Begelton can lose his spot to a FB. Or in that case they may like Tonyan for that role which puts Begelton back in the conversation taking Tonyan out of slot/wide mix for x number of downs.
9 or 10 OL? Do they like the potential of a young 10th. guy enough to want to protect him instead of trying to move him to the PS? With the OT situation behind Bakhtiari up in the air they may want to keep an extra one for more options as they work through the early games.
The thing that a guy like Begelton has going against him is that while he might look like a mid-round pick equivalent based on his beating up on second and third tier college players in Canada, he really isn't given his age. He could end up on the PS for deep bench. They probably know if and how many other teams had an interest in him as they would with undrafted rookies.
I've got him penciled in for a spot on the roster at the moment, but until you study the whole roster and get down to brass tacks as cutdown draws near, it's just a pencil mark, not ink.