Pokla, there is no doubt that ZJW is still at very high level. Those two reasons were cited from what YW said. The fact is that she said that, and it is also a valid reason.
She also mentioned the 2nd reason, I also said "more important reason", is that they don't have any Olympic ranking points yet.
Here is the 3rd reason which YW not dare to say, since it's against coaches wills, and they will not have any good result under current coaches. As you also said, they may still better than non-Chinese pairs, but this is not good enough. Only 3 pairs can go to the Olympics while now China has 4 strong pairs. One of them must be abandoned before the Olympics. If YW still teams with ZTT, she has the best chance in 4 pairs (most ranking points and also coaches' favorites), but if she teams with ZJW, they will be the most likely the one cannot go to Olympics.
Hope this helps