You got here late so to prevent you from wasting too much time, you should know that Dizzy loves to change the goalpost in an attempt to call a strawman, even admitting that he enjoys messing with "Yamato fans" to prove how "dumb they are."
Originally he said Yamato was gonna stay with Momo in Wano to protect it from its enemies. When people kept asking him to explain why Yamato will turn a complete 180 on going out to sea, he switched to saying Yamato will travel with Momo as he opens the world to Wano.
When asked how Yamato the guardian will protect Wano when she's not even there, Diz said the Scabbards can protect it while she's gone.
Obviously, we asked what's the point of Yamato staying behind in the first place if the Scabbards can defend Wano from its enemies, along with Yamato easily going to sea with Luffy. He proceeded to call us idiots and stopped responding.