Lan Wangji may not be able to perform Inquiry, but he still understands the interpretation. He does raise a brow because as far as he knows, Wei Ying doesn't know how to play Inquiry. But... he supposes he's done it enough times that Wei Ying knows the simple questions and simple answers by rote.

Not only this, but he'd played so much for him while he was dead. Perhaps some part of his soul heard his songs, wherever it was that he lay, imprinted not in his memory but on his soul all the same. Wei Ying, there are so many rabbits. Wei Ying, I will speak to shufu if you return. Wei Ying, Wei Ying. Come home.

Surely, those will be in his vocabulary.

"Ask them their names," he requests.