I love your eyes.
I understand they are trying to familiarize us with the second person plural, but I don’t see any instance where I would address a group of people and say that I like all of their eyes. Perhaps if I was under the spell of a vampire cult and about to get bit by one of them.
Welocme to the forum!
You are completely right … but … you will encounter a lot of these examples.
Clozemaster (or Tatoeba) has a penchant to choose those solutions that are grammatically correct but are very unlikely to be of any use.
See for example Le dita sono le vostre?
Actually, I am waiting for “Sono incinto.” 
On the other hand “Sono incinta.” spoken by a male voice is funny enough.
Perhaps a crafty Cloze way of ensuring we don’t forget the grammar here👀
Just imagine speaking to two twin girls who have beautiful, identical blue eyes.
On a more serious note, the plural form of the second person is sometimes or historically used as a polite way to address a single person.