I think the algorithm solves the problem of which photo, out of a set of photos, is the best one to show. So nothing has changed regarding the mutuality aspect, only which photo of the user is their best photo based on data collected from past swipes. In other words, they're continuously rotating through a user's photos, trying to find the one that gets the most positive feedback and showing that one more often than the user's other photos.
I think the algorithm would show which photo the "most" users would like is. What if you're someone who loves cats like no other and puts a cat on your shoulder (or wears a cat t-shirt or something). You're probably going to have a lot less "likes" than a "normal" picture of you, but the odds of you getting along might be much lower (I'm sure the average individual likes cat people less than the person who picked a person with cats in their picture).
It seems the shallowness of starting on the footing of what someone looks like alone kind of renders this point moot. If you're trying to identify compatibility based on who a person really is, their profile photo may be the least ideal place to start. If anything, I think this at least gets the user a foot in the door more often.
