User blog comment:FairyRaven/Fairy Tail Chapter 391: Gray vs. Silver, Review and Commentary/@comment-31.132.65.50-20140704183810/@comment-7418318-20140704222756

He was making a joke. And it's not about whether he likes to eat/drink blood. It's a matter of whether he can absorb it magically.

So far Silviora has only absorbed ice that was formed completely out of Gray's magic. Freezing something that was already there even without magic might be different enough that Silviora can't just absorb it magically.