That's not true either. Yoshida clearly said he was so focused on the details of the story that it ate into the final QA time. That's all. There was no issue (at least, not as a reason for the delay, though result of QA could reveal an issue), just regular development being delayed due to spending too much time on ensuring the quality of the story (which I personally have no problem with as the story is the main draw of the game for me).
The QA time is just even more important now with potentially so many more players who will be experiencing the expansion, but it's still what they would've done even without the delay.