Worked with Support today, and showed them that the 6.5 U1c ISO still does not work, meaning I still get the error. The tech reached out to some other people and the ultimate answer was that, since we aren't currently using Content Library, I could ignore and proceed past the error.
From Engineering:
"If they were not using Content Library on 6.0, they can safely ignore this warning. There is no further action necessary. They can also start using the Content Library after this upgrade if they so choose."
We have no timeline at this stage for when this article will be released.
So I went ahead, and everything seemed to work. I will do a more detailed checkout tomorrow.