> I rationalize this as the models attempting to compress as much into the fewest tokens

I'm not convinced about that. I just asked Opus to explain a bullet point from its research for me. The bullet point in fact had a 1-sentence explanation that was in a referenced article. What it gave me instead was 8 paragraphs and a table. Maybe it's my fault because I just asked it to "clarify point XYZ" instead of being more precise.