I don't know the details, but it is possible that they simply aren't allowed
by insurance to give demo flights to student pilots. Have they offered to
demo the airplane to you as long as you don't fly it?

The situation isn't exactly the same, but not many car dealers give demos to
customers who don't yet have their driver's license.

My advice is to cool your jets on buying an airplane and finish getting your
ticket. Flying your own plane just adds another distraction. Insurance
will be very, very tough to get. Keep your eye on the ball.

- Mark