Sounds like additional useless feature to further clutter the game.
A) based on the info you should get the shards at 500th pack (not sure where it is written but let's assume that is the rule), SO YOU NOT GONNA MISS IT ANWAY
B) if you are thinking that you have been cheated and not given shards or really want to know when those are coming up = just keep notes to yourself? Create .txt file or excel and add mark for every pack opened -> sum those up
Not sure why game should have such additional feature built in.
Maybe the only clarification from EA would be nice if those "extra" event packs count in or not, because now when feature "open many" at the same time is present, for some reason you can't still open them all up of you say have X "regular" packs available and Y "event special packs" -> I might assume that those extra do not count towards 500...