Bill Z & Frank
My line of thought on this matter:
The trailing edge of the keel tapers and is very narrow. I think the caulking washes out over time. The keel studs are located further forward and the caulking there remains intact, thus sealing the bolts. If the keel stud nuts are tight and water is leaking into the bilge, there is a problem.
Perhaps some other owners might speak up regarding this. There is no way to know to know for sure unless you were to haul the boat, drop and rebed the keel. I took the gamble, but I also got a good deal on my boat.
One thing I would look for is stress cracks in the fiberglass near the aft part of the keel to hull joint, inside and out, indicating a hard grounding. Particularly if you have the deep draft model.