That CL language is only slightly more aggressive in terms of ownership than the Medium terms. All CL did there was add the ability to enforce against competitors scraping CL pages and reposting the content on their own sites to bootstrap content, a problem CL has been plagued with from many would-be usurpers and parasites. The author of the ad still retains general ownership of the content. You can legally post something to CL and then post the exact same text to eBay or wherever else, CL is not taking that right from you under those terms. As long as you are the one doing the reposting (not a parasitic third party scraper).
Language that takes full ownership would be the kind of thing you'd see in a work-for-hire writing contract, which looks something like this:
> The copyright for all Work produced under this agreement shall belong to the Client at all times. Client shall exclusively own in perpetuity all now known or hereafter existing rights of every nature worldwide pertaining to such Work in or as part of any version of the Client’s publications that are published in print or displayed through computer-assisted and other interactive media such as the Internet and World Wide Web (collectively the "Rights").
Language that takes full ownership would be the kind of thing you'd see in a work-for-hire writing contract, which looks something like this:
> The copyright for all Work produced under this agreement shall belong to the Client at all times. Client shall exclusively own in perpetuity all now known or hereafter existing rights of every nature worldwide pertaining to such Work in or as part of any version of the Client’s publications that are published in print or displayed through computer-assisted and other interactive media such as the Internet and World Wide Web (collectively the "Rights").