I'm not sure how you can equate building a startup and selling to a bigger company as a great interview for developers. Maybe they have great engineers, but IME it's far more likely they've got good founders, marketing or sales on top of (perhaps) some stellar engineering.

All that's moot though if your fundamental premise is wrong. Why does Anthropic need "the world's best software engineers" to build on top of the models? Compentent developers can build APIs - sorry - MCP servers and other integration plumbing.