We've had confirmation from the club that the wording means if you defer, you will be guaranteed your seat in 22/23 unless they have to remove it for some reason (e.g. expanded disabled bays, new hospitality offerings, some other ground works).
So even if you renewed and that happened, you'd still have to relocate. They won't sell it as a seasoncard to someone else.
Typical City. If there's 99 correct ways to explain things and 1 shit one, they'll pick the shit one every time. Their communication skills are absolutely fucking awful. They should have either explained fully or said nothing.
So you can safely defer.