Okay so I don't know if you've read the study or not but the methodology used was to show people who answered an online survey (not just drivers) two images and then asked them which they thought was less human. One image had a cyclist with a helmet and another without a helmet.

So the study found that everyone, when comparing two humans, one with a helmet and one without, found the cyclist with the helmet to be "less human" than the one without.

The study has no empirical evidence for drivers considering cyclists less human than anybody except potentially for cyclists not wearing a helmet.

If I were to elaborate on their conclusion that the obstruction of human like features, such as face and eyes, I would make the argument that perhaps everyone sees a driver in a car as less human than a cyclist. I would also bet that the methodology they used in the study you provided would support this.

And judging from the replies by people in this comment section I would not assume that they are immune from the effect of lack of vision to facial features reducing their ability to consider the people involved as human, nor would I say I need to educate myself to the standard of people who can't click a link to a study and instead just read a clickbait, confirmation bias article.