Yes IK, I been an IFATC for 4 years now. It all depends on different factors. If the plane uses a RET you can clear them early for TO if needed due to the next arrival. As you know sometimes airports are busy and it is needed to fit many aircrafts on 1 runway. To make sure there are no GA’s it wouldn’t make sense to wait for an aircraft to fully cross the line and then clear to other for TO. Because as you know, Arrivals are top priority. (This only applies for really busy airports with tight spacing obviously).
It is part of our job to make decisions for ourselves to see if it save, strictly following the manual at all times would mean we should be replaced by robots.