I would say that's a bit of an exaggeration.
89db isn't super sensitive, even for a 10"
And even then Hoffman doesn't say you can't have LFE with a higher sensitivity driver...only that the enclosure needs to be larger //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif Not to mention with the added affects of cabin gain/transfer function, LFE isn't too large of an issue.
But in the end I agree that worrying about sensitivity for subwoofers is generally overrated. As Immacomputer mentioned...the enclosure is going to be a dominate contributor.