Have any of them actually done a transfer? If not, they may be mistaken.

Try this. Go to http://www.capitalone.com. Note that the "Miles One" link says Earn miles on your favorite airline. Click it.

The page it takes you to says ANY major airline. Click the Program Benefits link.

That page says:
The Best Way to Earn Airline Miles... Like many other travel programs, you earn one mile for each dollar you spend on purchases with your MilesOne card†. But what makes this program unique is its flexibility. With the MilesOne program, you'll discover the advantages:

Choose any airline—travel on any major U.S.-based domestic or international airline...

It's only when you to click the "Questions" page or the "terms and conditions" that you discover that your MilesOne miles can't be transferred to any actual airline. It's easy to see how a less saavy consumer could be misled/confused.