It's cause the loaner is WHIPPED.
Remember, transmission and engine have adaptive software. If you run it full tilt all the time it'll shift thinking you want full tilt all the time. My 99 328i auto used to be the same way. If I didn't drive it hard consistently it'd start shifting slow. Then I'd kick it around and it'd be back to good.
Experienced the same thing when I got a 330ci 5spd loaner. WTF?!? Shifter is nice and smooth, no notchiness into 2nd or 3rd, clutch is super easy and light. But it was pretty evident the thing had been *beat* eventhough it only had 7k on it. Everything was nice and loose because it'd been used a lot harder than I'd ever use mine.