No idea if this is still an issue. Scott doesn't work here anymore, btw.
I think the idea was that querying for the certname field with a value that would not match would return a 500 vs an empty result set. If you're saying that no longer causes a 500 then I'm happy to see this closed as "Cannot Reproduce". I don't know if the "a node that has submitted its cert but not had it signed yet" is applicable (I don't think fact or report submission happens until after a cert is acquired).