That's the crux of the decision right there. With separate pages the questions might not get the attention they need, but at the same time the separation would probably help the nature of the responses they get.
With an option it would have to default to being the same as it is now, and I'm not sure that the option would be used by enough of the people who could benefit from it to make a cultural impact on the questions.
I'm on the fence about it myself, but I think the option route wouldn't achieve the goals (of better separating topic types by purpose), but that might be helpful to a small amount of users who like the additional control over topic filtering.
One thing to keep in mind is that there are other topic types planned. For example, there will be a url topic type, customized for the recommendation of articles, videos etc. When there are more of those it might make more sense to have separation.