What constitutes a tournament?
How large a field constitues a tournament? Is 2 enough? Or 4? Some events had very small fields. Is 8 acceptable? If you're including Masters or WCT Finals that seems a minimum cut-off. It does make records of titles difficult to compare.
What we can be sure of is that there are many, many matches lost to history. Is it really possible that anyone has played more competitive tennis than Rosewall, Laver, or Gonzalez? In the open era Connors is the benchmark for longevity but we don't know what we don't know about the four past greats.