Bonjour,
C'est précisé de manière explicite dans le green book :
Appendix 1
7. Thirteen Orphans (88 points)
Hand is composed of singles of any 12 of the 1, 9, and Honor tiles, along with a pair of the 13th.
Does not combine with All Types, Concealed Hand, or Single Wait. (Combines with Fully
Concealed if Self-Drawn).
A+