I'm pretty sure you aren't allowed to have the whole ground sold out to season ticket holders in England. There also needs to be enough room to move people from the south stand for cup games.
https://www.ccfc.co.uk/news/2024/march/news-sky-blues-fans-to-be-in-south-stand-for-all-remaining-home-games/
Good to have an explanation for why the away fans can't be moved
I doubt the club will want to move legends day, sales look decent and I'm sure hospitality has sold better than usual. As well as ex players already booked. Could be lots of refunds