I am not even sure it is true.This really is TFC in a nutshell
In sports where there is a top quality Great Britain team, like swimming, cycling or field hockey, there are plenty of Scottish players. Glasgow Warriors are one of the best rugby teams in Europe and the national team is competitive nowadays.
Scotland has difficulty fielding top quality teams in multiple sports because in a country of 5 million there is not the depth. It is harder to explain why England are so poor with 55 million to choose from.