Well, why not, for heaven's sake? A speech impediment, perhaps. Imagine a cross between a severe lisp and a roar. That would be difficult to understand. But not impossible. The claim is that we could not understand him. Very well, who are we?

Perhaps we are the English speakers. Of course what we could understand would depend upon which language the lion spoke. I couldn't understand him, for example, if he spoke in Basque or Hittite or Old Icelandic. If he spoke in Spanish or German, I might be able to puzzle out a few words. But I don't understand anyone who speaks in Basque or Hittite or Old Icelandic. I have friends who do, however.

Of course, he might speak in Lion, in the language of the lions. That would indeed be difficult to understand. I don't even have any friends who speak in lion. So perhaps then we could not understand him. (Perhaps then lions do speak—in the language of the lions. Would that be worth looking into?) So we should need to learn the language of the lions.