Just food for thought, but Americans may make better AC systems. Some $15,000 US Cars have better Ac systems than $60,000 MB's.
I think it is because Americans prefer AC and even ice because they can afford to as compared to Europeans. When I was in Italy AC and ice (like in a drink) were not used and were only preferred from the upper class / tourists.
Maybe and just maybe that is why your Olds gets cooler sooner - comfort is more important over here. In any case, your AC sounds fine 2 me.
'89 420 SEL
'90 300 SEL
'68 Olds 88 Convertible
'84 300 SD (sold it)