I had a similar experience as before buying a(nother) car from CarMax today.
Told my CU what I wanted to do, and the agent emails me back with a preapproval for $50k, again without running my credit. Rate quoted @ 3.65% for a used car, though I'm not sure that included the direct payment withdrawal discount.
So I'm out at a CarMax in BFE, and unlike my prior experience, they refused to hold the car for me, even though I was willing to sign a purchase contract. I've been looking for months to find this car, and I didn't want it to get away, plus it's a long drive back from BFE, so I finance the whole thing at CarMax. After running my credit (bummer!) they gave me a 2.95% rate. I intend to just pay it off in 2 days with a check from my CU, so I fax my CU the purchase agreement, and my CU comes back with 2.99%, which is their absolute floor per the agent, and still without running my credit. Close enough. I drove home in my forever vehicle, and I'll pick up a check from my CU tomorrow and pay off the CarMax loan on Saturday.