If the LAG really will bet 90% of these turns who's to say BB isn't going for a c/r then gets worried when you do it and decides to call down? Against a relative unknown I think this suffers from too much FPS as I doubt BB raises the flop with total air if he's not going to bet the turn. He might have had a flush draw with overs but otherwise it's sort of an odd line on his part. I really think he either was on the flush draw with overs trying to clear outs or was going for the c/r on the turn with a LAG to his left and got worried by your strange actions.