Sometimes we get questions which are "theoretical questions in computer science", but are not "theoretical computer science" questions. Other areas in computer science (e.g. computer networks, ...) also sometimes study theoretical questions (formulated in rigorous mathematics).
Although these questions are not typical topics in theoretical computer science, they are theoretical questions that a theoretical computer scientist may find interesting and can answer. So I don't think being welcoming to them will cause a problem. What do you think?
ps: obviously the usual research level criteria would still apply to them, e.g. if the question is of the level of a typical undergrad course/textbook exercise then it will be off-topic.