I think Crisi meant 'uh-oh' in the sense that if your plans aren't firm, and may change as your trip approaches, renting may not be a good idea for you.
DVC villas get booked up quickly, especially certain room types or certain times of the year. It can very difficult to change resorts or change to another size of villa - impossible, in some situations.
Also, if you need to cancel or downsize your trip, the owner may end up losing their points, depending on the timing.
For this reason, many owners have a "no changes, no cancellations, no refunds policy".
Here's a possible scenario: You book a two-bedroom villa and a studio for a week, because you figure your kids and the grandparents are all coming. Two months before your trip, you find that one of your kids isn't coming because of school commitments. A month later, one of the grandparents develops a health problem, and both grandparents decide not to come. Now you no longer need the studio, and could get by with just a one-bedroom.
As a renter, in this situation, you probably wouldn't be able to make any changes, and would be stuck with a studio that you can't use, and a 2-BR villa that you don't need, and no way to get any of your money back.
In short, if you need flexibility in your travel plans, renting may not be for you.