With regards to the ToS, is that your interpretation? This is the actual text I find there (the last statement contradicts the notion they would sell our content):

“You own the rights to the content you post on Medium. We don’t claim ownership over any of it. However, by posting or transferring content to Medium, you give us permission to use your content solely to do the things we need to do to provide Medium Services, including, without limitation, storing, displaying, reproducing, and distributing your content. This may include promoting your content with partner companies or services for broader broadcast, distribution, or publication.
We will never sell your content to third parties without your explicit permission.”