While the rule seems to contradict itself, it's important to carefully consider the specific details and interpretations within the game system.
In general, rulebooks strive to provide clear guidelines and restrictions to maintain game balance and thematic consistency. However, exceptions and special cases do exist within game systems, often due to unique abilities or mythological elements. In the case of the sohei warrior monk mentioned in the Swords for Hire list, it's possible that their inclusion may be an intentional exception to the general rule regarding Sohei Buntai.