good swap???

If this deal were to happen right now, CGY probably needs to add, maybe Kylington? Just because Reinhart has produced more. However I feel Bennett can be more impactful if he isn't producing (like now) but Reinhart tends to disappear when he's held off the score sheet.

Why on earth would buffalo make that deal?

Because sometimes a team has to come to the realization that certain players just aren't going to mature and fit within that specific teams system.
I think moving both of these kids might be just what they each need to light a fire under them.