Yes it is very possible to have a leak and still achieve target boost if the wgdc tables and turbo dynamics will allow.
Keep in mind the ecu doesnt change target boost based on af trims. It has a target and will do everything within its power to achieve boost which includes over working the turbo to get there *ie pumping boost right out a small leak*
Obviously a gross leak will cause you to miss target boost because the lack of ability to build up the total pressure needed.
Hope that helps and answers your question.