Here's the thing about back swing speed: It can make or break your stroke timing. It can also make or break your ability to actually 'see' what you are supposed to be looking at.
In short: Beginners and even many intermediate players have an inconsistent backstroke speed, and generally, way too fast. As a result, they miss a lot.
I encourage a consistent, slow backstroke speed, regardless of the forward motion speed. Do top players bring back their cues at exactly the same speed all the time? Probably not. But it is a pretty consistent speed with a few exceptions.
So encouraging beginning and intermediate players to slow down their backstrokes and try to develop a consistent speed is the first step in breaking a very difficult unconscious bad habit. Yes, unfortunately it has to be conscious for quite awhile until a new neurological pathway is embedded.
But a slow, consistent backstroke speed is good place for any player to start. Then they can tweak it from there.