Where did you get that nonsense? OK I googled it, "Improperly spaced edge" is exactly the same thing and same cause as a "shifted" edge lettering, just to a larger extent. I still don't consider it to be a significant error unless it has shifted so much at a fair portion of the edge lettering is missing. Even then to me it is mainly a curiosity
I believe the Improperly Spaced edge lettering attribution is rare. The error is actually a PEL, or partial edge lettering. Why they didn't attribute it a PEL I have no idea. Never heard of Imp. Spaced before. I have found tons of Grant PEL's since. More than any other presidential dollar. They are indeed not rare. Slipped edge lettering errors are even more common. I guess I got a little too excited when I seen a new error attribution.
Where did you hear this from since I've always heard that the US Mint actually does the edge lettering.
The main thing to realize is just because a coin has an error doesn't make it valuable. Plating blisters are an example. Sure it's an error, but who pays a premium for those?
Update: Leaving for Mike Diamond 5 of them .. Going in for further study, free of charge .. Should be interesting, at the least ....