I am not terribly surprised that CAT scores may be lower than SATs - CAT tests do not so much measure what the school has "taught" them, they are more a measure of ability.
Furthermore, the scores are not reported nationally, nor put into league tables, so schools do not feel the need for all sorts of shenanigans to make them look better.
DH is a Deputy in a comp, and he feels they give a truer indication of ability, whereas the SATs scores can be massively overblown for individuals.