Yes, it’s a strange setup 🙁
A user of level 4 can add, edit, and delete categories (!) = changing the whole structure of the blog, but a user of level 9 can edit only his Pages and those created by users of a lower level.
I gave up a long time ago to find any logic in the user level system…
As a Level 10 User I have no problem doing create a new page with Write->Write Page. I also have no problem doing Manage->Pages and editing or deleting Pages.
If you have more than one Level 10 User you could have problems like what you’re seeing.