I think it's a little bit too much no?....

A developer has replied to my review of add-on xStyle.:
- Tabs and webNavigation:
to listen the tab create and update events, and insert css or replace css for the pages.
- webRequest and webRequestBlocking:
for "modify CSP headers".
- contextMenus:
Add right-click menus into browser's menu.
- storage:
Storage all styles and settings.
- Downloads:
expoer styles.
- *://*/*:
get permission to insert css to all websites.
- clipboardWrite:
auto copy md5 value when export one style

It is more clear now ... just a little bit more because i am not a coder
;-)
AMO need to add a page where these explanations can be found directly when we show the Permissions in their addon pages.