To be honest, i don’t think politics is a concern here for Cock.li but rather reliability and security. Smaller providers don’t have the resources to manage large amounts of users compared to established companies. I don’t think it is inherently a political service, it just happens to be popular with users who need anonymous throwaway emails.
Riseup on the other hand is meant to be very political but also suffers from the exact same problem of being underfunded. Being invite only also does not help.