I don't see how their supplied vector data for the roads could have been so perfect and accurate, yet the text directions could be so wrong.

I do. I find a Euro-centric map site a few days ago that included maps of the U.S.

It had an error I saw on mapsonus a few weeks ago (but I guess someone since complained about)

It picked the wrong fork on the PA turnpike at breezewood and had you get off, then get back on at the next exit.

I suspect they're using raw or perhaps out of date TeleAtlas data.