contrastedly if I was to ask an unconscious person people would tell me to assume they don’t want a glass of water and that I shouldn’t pour it down their throat

This is exactly my point! When given neither direct consent nor direct non-consent, we assume non-consent. The difference is I apply this same logic to an unborn person, and you don't. Why not?

and again if I was to offer a non entity a glass of water it could neither want or not want said water as both presuppose existence

In this case it wouldn't make sense to involve an unborn person because the question being asked is a question exclusively for existent people. But the question of whether to bring a person into existence is a question exclusively for non-existent people; it wouldn't make sense to ask that question of an existent person.