The classes' "stances known" sections say Warblades specifically have to take Warblade stances, and Crusaders have to take Devoted Spirit, Stone Dragon, or White Raven stances. Swordsages however get to choose "from any discipline open to you."
Does that mean Swordsages can pick stances from ANY discipline provided they have the prerequisite maneuvers from Martial Study or Master of Nine prc?
Example:
Swordsage 13/Master of Nine 5. On becoming Swordsage 14, are they limited to Swordsage Stances or can they pick from ANY they have prerequisites for since Master of Nine made ALL disciplines open to you?
Edit:
Sorry, about the confusion. I fully understand how PRCs work when you take a new level of the PRC. The question was about taking a level of Swordsage AFTER the PRC and how the wording of the Swordsage entry not specifying that you can only pick stances from Swordsage disciplines but rather from any that are "open" to you.
This is noticeably different from the Warblade which unambiguously says you can only pick stances from Warblade disciplines and the crusader which lists out all the disciplines which you can choose. It's also different from casters that specifically state that the spells they cast come from the [class] spell list.
So upon gaining Swordsage 14, can I BASED ON THE WORDING choose a Devoted Spirit stance if I already have 5 Devoted Spirit maneuvers in my list thanks to the previous PRC levels?
NOTE: stances only count as maneuvers for the purpose of prerequisites, otherwise they're their own thing. That's why Warblade and crusader restate the discipline limitations in both sections.