The idea that the best player may not take the most shots may be an accurate argument in favor of others having more attempts, but with FT being team-trained both through regular training and facility, the assumption that the player best elsewhere on the court will always have best FT% isn’t always the case. In fact, the player on my team who is by a wide margin the highest in salary and skills at his position, is currently 3/11 (.273) from the free throw line on the season.
This would support the theory that if he has more touches vs weaker opponents and more attempts, my percentage would be lower- however, it does reject the idea that better teams would have a lower opponent FT% because he’s the Shaq of US III.4 when he’s at the line.