It's not just Arendelle in fact most of the New Disney Worlds introduced to Kingdom Hearts III (minus Big Hero 6) also had guidelines from Disney as well, even Pixar also put guidelines to Nomura and Square Enix on the worlds based on their movies (Toy Story and Monster's Inc.), of course not in the same level as the guidelines seen in the Tangled and especially the Frozen world, but it was mostly noticeable In the Monster's Inc. world given how picky and restrictive they were on not allowing Randall to be a boss (more so a mid-boss) in the level, compared to the Toy Story world imao. I say that San Fransokyo, from Big Hero 6 was the ONLY new Disney world out of the 5 new Disney worlds (Kingdom of Corona, Toy Box, Monstropolis, and Arendelle) introduced in KH3, that Disney didn't put Guidelines and restrictions on given that the story was set after the events of the movie instead of being a retelling of the original film which allowed Nomura and his team creative freedom, of course credit goes to Roy Conli (producer of Big Hero 6) who came up with the original story.Agreed. We might think it's ridiculous because we're all KH fans, but I can see it on the other side too. Disney is a multi-generational company that thrives on maintaining the magic that's in their IPs. And kids went nuts over Frozen. To this day, the most popular Disney costume is Elsa. Do You Want To Build A Snowman is a song these kids know by heart, and parents understand how popular the movie is just by seeing their little ones lose their minds. So imagine how Disney is feeling when it comes to this. They're probably not willing to take as many chances, and especially because Kingdom Hearts as a franchise is getting a lot more popular now. So even though we probably originally had a more fleshed out Arendelle, Disney probably saw the money come in and didn't want to take ANY sort of risks.
It's a shame, because Arendelle would've been the perfect world to start diving more into the New Seven Hearts, but at least we know Elsa and Anna both are part of the Seven. So it's not like we'll never see them again, and hopefully the next time, they'll be more lax.
And it would be a shame too because of the really cool movies coming out, but if it's going to be a huge stress on the team going forward, I'd rather them pull from older material instead. Even summons like Simba had to be "different" because of Disney, and they never had an issue before.
Lastly, I feel in my unpopular opinion that Kingdom of Corona was more frustrating than Arendelle. I already made a lot of complaints on Kingdom of Corona, before which you can view here, here and here. But frankly I was more frustrated with how Sora, Donald and Goofy stood out like a "sore thumb" in the world and literally don't know what has happened especially during the 2nd and last acts of the world.