It's in the first sentence of your quote:

"our continued collaboration with Anthropic"

Read this as: "we get discounts, rate limit increases, a direct line to responsible product managers; in exchange we participate in friendly marketing." It's extremely common in this line of business - typical of database vendors, software tool companies, etc.

This is more in response to my original post, but okay interesting point. (When I said "invested" here I meant invested in finding security flaws.)

Conspiratorial nonsense

In many countries it is mandatory to mark any form of compensated advertising as such. If your claim is true they might be breaking some laws here & there…

I would expect Firefox to be less invested in this than Curl. Firefox is aimed at consumers, Curl is embedded in a wide variety of products.