Given the lack of clear communication and the fact that their primary competitor openly supports the use of bespoke harnesses, I highly doubt this is an incorrect announcement.

Anthropic is destroying goodwill that is hard-won in this space. At the end of the day, people just need to do their work in a way that makes sense for them. In my case (someone who has been building ML/AI tools for 25 years @ MS & Apple), I have much better results using my bespoke harness. If I'm paying $200/month for compute, I should be able to use it in a way that works for me. Given the push back, I'm not alone.