getSize() returning too many often -1

I've came accross the well known behaviour of query results returning -1 when asked for getSize().

While this is ok for optimization reasons (lazy results fetching), I just discovered that the default "resultFetchSize" value in lucene queries is Integer.MAX_VALUE, so in all queries I've ever executed, all results were actually fetched before asking for getSize, so IMHO nothing prevents getSize() to return the real value instead -1