Well, I was hoping someone else would answer - not that I don't have an answer, just that I don't think it is very 'elegant' 🙂
Just in case you're still waiting for an answer, there is a simple solution, and here's what I did, in brief--
- ran a summary statistics on the field I want to sort symbology on (you don't have to summarize anything, just run it to get a Count field)
- joined the resulting table back to the orig table by the same field you summarized on... (I think you may have the idea now?)
- that'll give you something in the orig fc to symbolize by via 2 categories, the new 'count' field and the orig field...
- here's the trick, I guess you might say, the sort order can be reversed by clicking anywhere in the symbol window (after adding all vals) -- simply right-click and select 'reverse sort'
Hope that helps - let me know if you have difficulty.