Yes. The system cannot check for time dependencies. This is a non-trivial issue and even subject to current research. If it indeed happens that both the seminar and the lab course are at the same time, then this is a credible case to speak up to another course organizer and ask for admission to his course (which does not overlap). We have asked course organizers to provide some flexibility for such cases, but there were few.
At least now you learn early which courses you have been assigned to.