Yes, the data really does hold up. We ran the data on 30,000 videos and the work took a long time. We believe the findings are correct. Thanks! -- Dane Golden, a co-author.
Hi Emeric - Of course you're saying this to be funny but let me geek out for a moment here. Actually the practice you're referring to will not get you more views UNLESS there is actually one or more attractive women throughout your video. But YouTube is interesting, because if the video is too spicy, it may get flagged by the community as "inappropriate," which means that the YouTube algorithm will show your thumbnail less often (or not at all) which makes it more difficult for you to get any views. Also, if you do not have what's promised or hinted at in the video, viewers will watch for a few seconds and then leave the video and not come back. This is actually the worst thing for your video because a shorter-than-average "watch time" will downgrade the ranking of not just that video, but your entire channel. The "hot girl thumbnail" technique was used a lot by some people until perhaps 2013, when YouTube changed their algorithm to prevent this. Otherwise it probably would be a lot more common today.
P.S. I am the co-author of the study mentioned in this article - it's called "Harnessing the Power of 'You' in YouTube," by TubeBuddy and HEY[.]com, if you'd like to read more. Thanks!