Seems to be an audio error.

There seems to be an audio error in the Dynamic Queue where some champs, like Jhin, doesn't "say" their pick lines. I've also noticed this with Sion and Rek'Sai sometimes losing their Dialogue in-game. I have no way of showing you, but I do know that it has happened to me a few times and I triple checked my audio, and it is working 100%.