So another question is "Is this good for the hip to be popping it out to test it?"
Doesn't seem like that would be a good thing!!!!!!
I don't think it's a good idea to intentionally dislocate a joint either!
Even if it pops out easily, it's not a good sign, but in itself doesn't mean the dog is going to have hip problems. A dog can be evaluated as "fair", "borderline", or even "mild" just because of subluxation with no DJD present.
As far as I am concerned, if the sockets are deep enough and the heads are nice and round I don't think the dog will have hip problems. If the sockets are shallow, I don't care how tightly the heads are seated, I think they are going to develop DJD as the dog ages.
The OFA evaluates several things before grading a set of hips:
http://offa.org/hipproc.html
I have my doubts about this "hip pop test" meaning anything at all. I just don't think it is a repeatable, scientific process.