Correct. Brackets around a 4 are no recognized as chord syntax.
This is a list of all known chord extensions: maj, maj7, maj9, maj11, maj13, maj9#11, maj13#11, 6, add9, maj7b5, maj7#5, m, min, m7, m9, m11, m13, m6, madd9, m6add9, mmaj7, mmaj9, m7b5, m7#5, 7, 9, 11, 13, 7sus4, 7b5, 7#5, 7b9, 7#9, 7b5b9, 7b5#9, 7#5b9, 9#5, 13#11, 13b9, 11b9, aug, aug7, dim, dim7, sus, sus4, sus2, sus2sus4, sus7, sus9, -5, 5, +, +7
I can add standard extensions but not uncommon stuff like 2 which should be add9 if you go by the books.