Customers care about model output being correct, Anthropic cares about model output being generated by Anthropic model.
This solves for the latter with a bunch of handwaving for the former. The end goal is gonna be FUD for cheaper model routing because that obviously is at odds with their biz model.
You developed your agent implementation and more importantly, evaluated it, against a specific model.
You don't want all you eval work to go to waste just because the discount inference provider you're using decided AcmeModel4.23 is as good as the Anthropics GilgameshEpic7.2 that you used to validate your solution.
We already have trouble enough with model retirement.