Comment by amluto
No, MV3 really isn’t more secure. MV3 still allows extensions to inspect your requests — it just doesn’t allow extensions to block them.
It’s almost comical how weak the security/privacy argument for MV3 is. Chrome could have developed a sandboxed web request inspection framework to prevent data exfiltration, but they didn’t even try. Instead they nerfed ad blockers without adding any security.
I remember that another comical argument was performance. Supposedly, having extensions run in the background all the time is bad. So it's better to constantly, completely re-initialize them whenever an event wakes them up.