It will be a miscarriage of justice if Jennings does not win his suit. First off, he didn't match the description. The caller identified the suspect as a "young black male." Jennings was 56 at the time and looked the part.
Jennings identified himself as Pastor Jennings, told them where he lives and explained that the property he was on is not his but he had been asked to water the flowers (which he was in the middle of doing) while the home owner was on vacation. The interaction should have been over at that point since the cops had no reasonable suspicion that a crime had/was occurring.
If the cops were still generally suspicious then they could have continued to observe Jennings behavior or contact the caller. Demanding physical ID at that point was totally irrational.