I actually have real trouble with this kind of thing. If someone says they can’t X because of Y, and that is all they say, then I assume that’s all they mean. If I want X, then I will do all I can to get not-Y. And if I succeed, I assume the problem is solved. If there are multiple reasons why X is not possible, I would rather they told me all of them. If they are saying Y because they don’t want to give the ‘real’ reason.. well, I would rather they just told me the real reason. Even if it’s something ‘hard to hear’ or supposedly upsetting, like “I don’t like you”. It makes me angry if I go to great lengths to fix Y and it turns out Y wasn’t the reason after all. I realise this is a problem, but it’s really difficult for me.
It sounds like maybe you’re assuming that the default answer is yes in situations in which you ought to assume that the default answer is no.
In situations in which the default answer is no, no-because still basically means no. Because they didn’t actually owe you a reason, to begin with, and they might not even know all the reasons or want to examine them.
In situations in which the default answer is yes, it’s different. Then, no-because is more likely to mean maybe-if. But it doesn’t mean yes-if until someone actually *says* yes-if.
It may be useful to think of “no, because X” as an intended-to-be-polite way of saying “I won’t even think about it, because X”. If you can figure out a way to make X not be an issue, that doesn’t make the answer ‘yes’; at best it makes the answer ‘I’ll think some more about that’. (Sometimes it doesn’t even do that, if the person really wants not to have to think about the question and was using X as a way of not having to come out and say that.)
That’s often the case, but not always.
I’d say that it’s good to keep in mind that it *might* be the case, and if you ask follow-up questions, do so in a way that makes it clear that you will take “No, and I don’t want to talk about it any more” as an answer.