They seem to have been rushed with certain releases. It is impossible they didn’t know or see this awful writing before 5 series.

Yeah agree. Someone on HN posed the theory that the dogfooding might have worked against them here - the theory is that internally they used Fable as conversational agent and Opus as subagents, leading to Opus falling deeper into a style mainly aimed at other LLMs.

All conjecture of course, and yeah it's hard to imagine they would enjoy this prose internally