This is actually because of the way the default is set up. It still registers it as a thumbs up (you can see it when you hover over or click on the heart) but the single emoji reaction default is heart.
I tried changing it yesterday to be the thumbs up and….it didn’t go well, lol, it broke the icon entirely. So it’s on the list of things to fix.
I will add it to my list of things to look at addressing, great catch!