There are some questions that need to be pretty broad. They fit the site, they follow the rules, but their implications inherently make them too "broad" because answering a bit of it will lead into a chasm of answering a bunch of othe questions.
For example, "What are the effects of higher gravity on a terrestrial planet?" This question can be taken as need lots and lots of explanation as little changes that this would effect would acculmulate and create a complex set of interactions. However, regardless of those complexities, we can still say things like "Mountains would be lower and Animals would be stockier, because the gravity pulls them down" and this could be more than enough of an answer for the particular question, because they're looking for the broad ramifications, not the "too many possible things to take into account" answer. I think this being possible and being understood as what is being looked for is acceptable. And it is much better than saying "no you can't ask that because there are too many variable in specific" when we know that regardless of all those variables you still get a pretty simple and predictable general general outcome.
So why not just add a tag that helps explain that the questioner is not asking for the nitty gritty details that they can fill in for themselves, but a more generalized answer? I think that without something like this it harms the ability for people to ask questions that would help them. In a scenario where I'm making animals that exist on or come from a high gravity planet for example, or are trying to describe features of such the important thing I'm looking for are the generalities, not the nitty gritty details. Adding a tag that says as much would just help, just like the "hard-science" tag, some people want to know all the exact details of the subject, other people not so much. I think having a tag would benefit people and would also help by having a contrast tag for ones like "hard-science" (which come to think of it is a bad name for it, changing it to something like "detailed" might be a good idea, because "hard-science" to most people simply means it is realistically possible within known laws of science, not that they want a ton of detail to say why it is, but that's another discussion)