They don't. I suspect you haven't actually read one of these articles in detail.because it is in no way a recommendation from TorrentFreak. It literally opens with this:

The VPN review business is also flourishing as well. Just do a random search for “best VPN service” or “VPN review” and you’ll see dozens of sites filled with recommendations and preferred picks. Some VPN companies, such as Kape, even own review sites.

At TF we don’t want to make any recommendations. When it comes to privacy and anonymity, an outsider can’t offer any guarantees. Vulnerabilities are always lurking around the corner and even with the most secure VPN, you still have to trust the VPN company with your data.

Instead, we aim to provide an unranked overview of VPN providers, asking them questions we believe are important. Many of these questions relate to privacy and security, and the various companies answer them in their own words.

We hope that this helps users to make an informed choice. However, we stress that users themselves should always make sure that their VPN setup is secure, working correctly, and not leaking. Also, we advise people to properly research the company behind the VPN service.

NordVPN appears first because it is a sponsor, as is clearly stated:

*Note: Private Internet access, ExpressVPN and NordVPN are TorrentFreak sponsors. We reserve the first three spots for them as a courtesy. This article also includes a few affiliate links which help us pay the bills. We never sell positions in our review article or charge providers for a listing.

The same questions are put to every VPN provider on the list. It is unranked - whether they first or last is completely irrelevant.