Not that I've set a google alert for Liam Hemsworth+Miley Cyrus but if he had talked about Miley/their relationship, I feel like I would have read about it.
Liam is currently promoting Paranoia. He's been on the morning show circuit, he's ringing the NASDAQ, it's a standard press tour...and Miley hasn't come up? Miley was certainly asked about their relationship, or at least it was hinted at, when she was pushing her single, We Can't Stop.
It's very possible that his publicists have thrown down strict instructions to media outlets about what they can and can't talk about, sure. Liam might not be as skilled as Miley is with a stock answer. (She just kept saying "I'm wearing my ring".) Or we can turn it into a gender discussion. Do men get asked as often -- when are you getting married, what about the kids, etc etc etc?
Anyway, if you have heard Liam discussing Miley on this current push for Paranoia, let me know because I must have missed that headline.