the stuff about EDN being natively supported by clojure is a red herring and irrelevant.
In the specific case, it removes the data transformation code required to convert the clojure data structures I have to sql, json, or xml that postgresql understands.
You can embed a JVM in PostgreSQL and write the functions yourself (or use PL/Scheme I suppose), but I would be basically amazed if anyone decides to do it for you.
JSON gets the nod because it's understood by billions of systems. Other formats are going to struggle.
I asked because I wanted to know if there was a particular reason for your wishes -- which is, as I said, quite parochial compared to the reach of JSON -- over other potential priorities. If asking questions is "trolling", I'll be over here with 4chan and Socrates.