Is it just the documentation that's a problem with that Richard, because that limit on finished matches was introduced a couple of years ago now.
I remember it being a minor nuisance at the time because it wasn't possible anymore to perform a simple loop over the endpoint keys of "registered", "in_progress" and "finished".
Returns this comment at the end of the string, following Registration matches.
,"comment":"Results are temporarily reduced to the most recent 500 matches for performance reasons"
This is not shown in the spec for the end point as far as I can see.