There is (apparently) some inconsistence in the meta filter values, regarding project search, in advanced filter mode.

Given a project A (which has subprojects)
Being current project: B (which also have subprojects)
Being in advanced filter view, and these selections in project field:

1) Select project A
result is showing issues from project A, only A and not any of its child subprojects

2) Multiple Select project A and "current"
result is showing issues from project A, and B (current project), but not any from their child subprojects (either one)

3) Select "current"
result is showing issues from project B (current) and also from its child subprojects.

So, case (3) seems to be inconsistent with the general rules of advanced filters.