>>107051277They already repeated with Alya and Nino so it's not like they're against that.
The episode summary (not the rumored spoilers but the confirmed early released episode guide to the whole season) says that Ikari Gozen is Kagami's mother trying to lock her away for defying her putting her in the perfect position to help out wether Marinette is still sore about her being a rival or not. This is also after Onichan where Kagami becomes akumatized because of Lila which might change Marinette's opinion of her.
Furthermore even if the spoilers are wrong, the production code for the Dragonbug and Snake Noir renders do confirm they're appearing in the finale, which would likely be all heroes involved similar to Heroes Day. Logically someone has to use the Dragon first as Adrien sharing with Luka right there, but Marinette running off to get the Dragon which has never been used before wouldn't line up right.
And really it would be really odd for Adrien's finale power up to be used twice before hand but Marinette's to just be pulled out for the finale only. Even if it's not Kagami the Dragon would have be used at some point earlier in the season for it to be called back to otherwise it would be Mousebug they'd use.
As for why it wasn't leaked, the render might not have been finished yet.
