Its not as simple as that. In some cases TA's are sent to the membership when the MEC and NC know they will be voted down. Sometimes the MEC/NC want a no vote on a TA for political capital, and sometimes the NMB even demands it in order to make progress or to get released. Its a lot more politically expedient to point to a fresh super majority NO vote than to continually take the word of half a table full of the same people every day claiming to speak for several thousand.

And sometimes the MEC/NC is just wrong. Rubber stamping a POS just because its a TA is far from an automatic, mandatory predetermined conclusion.