Nothing overly special about it, just my 1500th.



Wish I had counted mine now...
It's obviously kept and easily accessed (you can filter for visited/unvisited systems and so on) so it's literally just that they "couldn't be <bothered - original word got filtered> to do it".
The contents of any given system are generated on demand so no, this information is neither obviously kept nor easily accessed. That's how the whole proc-gen thing works.
It would be lovely if FDev recorded more stats like this in game for us but that wasn't implemented up front because other things took priority and retro-fitting it is not as trivial as you make out.
Plus EDD does a wonderful job of it. *shameless plug*