In prose, it can be more difficult (or even less legal j/k!) than it is in speech to gauge nuances in the author's intent. Depending on how a "what if I" question is phrased, it could be very difficult to distinguish it from a request for personal advice (pesak).
Mi Yodeya maintains an allergy to such requests for good reasons. Much of what we do here legitimately, with every possible disclaimer in place, could be - and likely will be - misused by people who choose to treat answers here as authoritative and directly applicable. I've argued in the past that this is a reasonable risk to take, similar to that taken by every public Torah teacher who isn't paskening. However, in incurring that risk, it's our responsibility to mitigate it however we can.
So, I think that the practice of not allowing questions that are phrased in a way that could be a request for pesak is a good one, one of the reasonable safeguards that we use to make it less likely that people will misuse our content.
That said, whether a question falls into that category is a judgement call, and there isn't necessarily a bright syntactic line that can be drawn between pesak-request-looking questions and not. In addition, the right thing to do in such cases is not necessarily always to close. If it seems likely that the question is actually a hypothetical that is just phrased in a way that makes it look like a pesak request, it'd probably be better to just do the requisite edits to make it more clearly a hypothetical.