This question may have different explanations, because the expression "everything in the black skirt" is not very common. However, according to the usual understanding, it may not mean confession.

Generally speaking, confession is to express one's love or feelings to someone, and it usually needs some clear words or actions to convey this meaning. The expression "everything in men in black" may be just someone's mantra, or a special expression, which does not necessarily mean confession.

Therefore, if you want to confirm whether this person is confessing or not, you'd better ask his real intention directly.