Ben Larcombe, the author of this wonderful piece, is not an expert at table tennis either. Can he teach someone to be an expert? Maybe, he can, but as a player he is not.
"My England ranking varies from about 150th – 200th depending on how I’m getting on at tournaments. My long-term goal is to get myself into the top 100 players in England."
This quote means that he claims to be an expert at table tennis because reaching top 250 is an "expert" level. Out of 1000 people who are ranked.