I have made a series of reference points in the center of faces. In a sketch drawn on a plane made with those points I can initially make constraints to those points by starting and ending lines to them. If I delete the coincident constraints and then try and manually apply a coincident constraint I am not allowed to.

In summary:
You can drag and make constraints to the reference points. Call this an implicit constraint.

You cannot apply constraints to reference points through manually selecting them and going through the constraints manager. Call this an explicit constraint.

So is this a bug or a severe limitation and should be reported as a bug?

I have sent it in to my VAR to see what they say.