When Sentinel was being developed, it was originally to have had a probe. But a chap from Boscombe, who was in the know, told me that it barely met its target spec without a probe and adding one would have been the straw on the camel's back.....
Allegedly when Raytheon showed Bombardier where they would be screwing a big agricultural refuelling probe on their sleek, lightweight Bizjet it took several minutes for the Bombardier chaps to stop laughing.