It's a little more subtle. and subtle is the point. Human emotion, heck, all of human experience is analog. Love for a child is different than love for a parent, for example. And it's fractally complicated. If you look at how a word, phrase or novel matches up to an emotion you'll see the flaws where it doesn't quite match up at every scale.
So, anyway, discretizing these 6 states and fast tracking them is ok, i guess. It certainly allows people to shade their like in an interesting way, but it blows away complexity. The simple like can convey more meaning, imho, based on the sender. A like from an ex-lover, for example has a different meaning than from grandma. In some sense, they're both "i'm thinking of you" but they're nuanced based on sender.
It's not super clear to me that providing the 6 states will actually convey more information. Really it just requires a bit more effort on the user. A guy hits like on a pretty girl's photo because of love or lust, same guy hits like on a fast car because of awe. The context is more than enough to infer the meaning. It does make the sympathy connection explicit, so that's something. The sad face is probably much quicker than typing in "sucks about the cancer, bro". Is optimizing that case for speed better for humans?