I reckon a decept part of that is due to American English vs. British English.
A great example of this is the Korean War, where a British brigadier in an extremely difficult situation told an American general "Things are a bit sticky, sir" - who interpreted it as "Could be better, but we're holding the line". The misunderstanding resulted in 500 dead and captured.
Is that really the same thing? We aren't just talking about understatement.
FWIW I’m not quite convinced there’s that much of a dialectical divide: “Not bad,” “he’s not wrong,” etc. sound entirely natural to me in American English.