I would never, ever, allow a vehicle to go 10,000 miles between oil changes, especially when short hop, stop and go driving is involved.
IMHO, 5k miles is the upper limit for your type of driving.
Never put much faith into anything a service manager/service advisor/service advisor tells you. About 90% of these guys are not mechanics, have no mechanical aptitude, and generally subsist on a little BS.
You're right, the oil does not break down but it will still be contaminated by the combustion process and water vapor, the latter of which is not always burned off when short hop driving is the norm.
Ask those service reps if they will give you a guarantee, in writing, about standing behind any engine problems if you maintain their 10k mile oil change standard. My guess is you will hear "Well, uh,..uh..I.. uh......"
For what it's worth, I'm an ex-SAAB tech and current SAAB owner (3rd one) and I would never agree to a 10k mile oil change regimen.