This meaning is not in LS but Bailly has it. In Stephanus, I have come across this meaning twice as in: εἰ δέ τις αὐτούς ἔροιτο καὶ πῶς ἡ εὐθεῖα λέγεται πτῶσις, etc.
πῶς is quite often used like this, as we might say “How come …?” or “How is it that …?”