Class E is a strange go-between. It is controlled for IFR traffic (IFR ATC services and clearances are provided as usual) but it is uncontrolled (in the sense that you do not need permission to enter) for VFR traffic.
So whether Class E is controlled depends on the perspective of the user.
At the end of the day, what you need to understand is that "controlled" comes in a number of shades. Controlled doesn't automatically mean that all aircraft are on an ATC leash and can only do as ATC says, and uncontrolled doesn't automatically mean that it's free for all, do as you please with no help from ATC at all. That's why there's a distinction in seven classes (A-G), and not just a single distinction in CAS/OCAS.