I like that you asked. While I don’t hold a strong opinion on it, I think you could argue that it is about consent.
I will argue more strongly than I feel because I think it helps to understand the point. (Assuming the person wearing makeup is a woman)
If you don’t know the woman, why do you care if she wears makeup and how she looks without? It seems like there isn’t a legitimate reason for it without it being a toxic reason, like “look! she isn’t prettier than me!” Vibe. Which is toxic for both people. Now it was a man who made the app. Now there is the hating of women for wearing makeup reasons but let’s ignore those. (Case: Unknown feelings of the woman)
If you know the woman and you don’t know how she looks without makeup, then that is clearly a decision made by the woman. Why do you have the right to expose her in a way that she doesn’t want to be. I mean some women don’t care if you see their tummies and others would rather die. Should you have the right to expose a woman’s tummy? (Case: Implied decision to not show herself like that)
If you know the woman and you want to argue that you have a justified interest in how she looks without makeup because she is a potential Partner (if she is a partner, you probably know already anyway). You could easily argue that you have the same legitimate reason to see her naked but obviously you wouldn’t think that it is a legitimate reason.
In other words, you shouldn’t care and it is kinda toxic to care; you don’t have consent to see them like it otherwise you would; you have no right to know.