I am very familiar with Kitsis and Horowitz, and Damon Lindelof (he is a consultant for OUAT). I am a huge LOST fan 🙂
While I do agree with you that the fact that Snow’s mother ‘died’ is essentiail to the plot, I honestly feel that part of the story was said and done, and that K&H left it up to us to understand that part.
I feel, at this point, they don’t need to go into all of that, as it would just seem like an unecessary sub- plot, imo.
As with LOST, I don’t think they are going to explain every little detail.
That is part of the big controversy with LOST, to this day. A lot of ppl say that they left too many questions unanswered, where as I feel they left some things to the viewers imagination/opinion.
They seem to be pretty straight forward with OUAT, which makes it a bit easier to follow than LOST was 🙂