Thanks,that makes perfect sense to me and it did cross my mind that that was a reason. But after the death of Lincoln, several members of AR's family were not exactly reticent about discussing and promoting the idea that the relationship was real, that it had taken place. If letters had existed between the lovers at all, wouldn't Robert Rutledge or Jean Rutledge or Nancy Rutledge have spoken of them to Herndon along with the (understandable)explanation that they had been destroyed?
As for the idea of no "overt courting", didn't her family and a few friends tell Herndon that AL had visited AR frequently, and that it was generally understood by everyone that they were an "item"?
And it still does not address the absolute cutoff of all communication with the family of the woman we are told was so pivotal in his life. That, along with the fact no one outside New Salem ever heard of this great romance, and he never discussed this allegedly key relationship ever, with anyone except for the disputed conversation with Isaac Cogdal in 1860, strikes me as very unusual.