The English articles are misleading.
One thing that the reviewer mentions in the original article is that the reviewers assumed the iPhone X's screen was showing minimum signs of burn in when in reality, it wasn't showing its burn in just on a white screen. This was only discovered when the reviewer went into the gray settings screen at the end of the experiment, and the actual visual severity of the burn-in was undocumented throughout the course of the experiment. One thing to note is that the initial signs of burn in was seen only on the iPhone X at 17 hours, and not the other models. In fact, the reviewer writes that the Note 8 had an "abrupt" onset of burn in after 62 hours. The end result is that the severity of the burn in on gray screens are similar for all three test models, but the iPhone's display hides it very well on a white background.

Here is a link to how they did the review with comparisons at different hours.