I believe you got that wrong.

Here's some extra context [0]: https://github.com/pypi/warehouse/issues/20927. Loooots of links to click in.

the point here being small service providers are _also_ able to get into this system, but I think there's an expectation of success.

The bar for trusted publishers is very high though. I don't think it's high "on purpose" to leave out certain platforms for being too small, but in effect if (for example) your provider doesn't have a security contact point then that's going to rule them out here.