That was just poor refereeing, if the ref deducted points early it might have changed. When refereeing comes down to interpretation these things can happen. I've seen fights similar in other divisions like Andre Wards last fight. Every division has a few bad fights, most of these midget division's are full of sprinters that doesn't excite me very much.
The welterweight division has better fighters. There's a reason only one HW is in the top 10 P4P list.