[Mitke]

Well yes, BB's play looks like pumping the pot with with a FD on the flop, then just calling with it on the turn when equity drops, and then leading the river to ensure it isn't checked through. I doubt you are ahead that 4% of the time.

BTN could have a set or twopair or the same straight as you do.

I think the biggest reason for calling in the end is, at least for me personally, that I'd probably go on a monkey tilt if I folded the best hand on the river in a pot this big. It is only a 1 BB mistake that avoids a lot of bigger mistakes from tilting...

And it is 6-max so give him the benefit of doubt.