That site says I'm at 6%, and I agree 95%+ is accurate. Some particularly obscure stuff is only on YouTube or Bandcamp, that's maybe 3%, another 1-2% is simply unavailable due to various licensing issues, generally odd albums for artists that have most of their content available. If you go way, way down the long tail of 400-youtube-view music from decades ago, most of it won't be available anywhere except YouTube and pirate sites, both with spotty coverage.