Sorry, Edward, if I was not clear enough...
How selecting top 8 players by rating to play a round-robin is better than selecting top 5 players by rating to play at the Olympiad?
The latest example:
Canadian Junior Championship that was last week in Toronto.
Top 10 juniors by rating competed in this event.
It was a great Championship!
But...
The previous Champion that convincely won Canadian Junior less than a year ago wasn't even invited to defend his title!
Why?
Because his rating isn't high enough...
We have already a tournament where the best Canadian players compete:
Canadian Closed Championship.
We need to use the results of Canadian Closed to select the Canadian Team.
To eliminate accidental anomalies we could use results for last 2 or 3 years.