Because, as Velax said, 'strategic secessions' for rule purposes have a very specific definition. The Secessions of Irombrozia and MR do not fall under the banned definition of Strategic Secession at all. They were not used to circumvent 'you can only recruit in the capital' restrictions for purely strategy reasons so that the realm (Riombara in this case) could better fight off their enemies, but instead were done because the Duke disagreed with the Realm and decided he was better off on his own. If you're seceding a Duchy and creating a new Realm just so you can refit closer to the front during a war, then you're violating the rules. That kind of requires the secessions to be friendly as well, as otherwise the main purpose is not to circumvent this ingame restriction.