This is one of the annoying things about the yes/no checkbox. In the state of a greyed out checkbox it is similar to a filled in checkbox that in other programs indicates multiple or undetermined states. Revit doesn't want to presume what state you want. If you run a schedule of the parameter I've always had it report as "No". When placing an item try unchecking the box before placement. You will probably have to do this for each category, if not each family, but it could work if you are placing multiple. You can also run a schedule sorted to allow you to uncheck multiple boxes at once.

I've submitted part of the issue to the Revit Ideas forum here: Clarify graphic for undetermined checkbox state - Autodesk Community

Hmm, I see. That's kind of what I figured. I guess I'll have to deal with it as it is. Though I did notice that when I uncheck before placement it does seem to remember that when I place new similar objects. So a bit less annoying.

Thanks for the reply and insight!