Mine has never had an interim oil change as its never done 6000 miles in a year .... Normally 3000ish.
This one has done about 7k a year so I would probably not let it bother me.
Like its been said, there is no space to say if its been done or not. They could just say yes and you would be none the wiser.
The CZt doesn't have the interim and their spark plug change interval is 100k apparantly
I'm sure if you asked some other BRABUS owners, they wouldn't have been so worried.
The engines are rock hard and can (and have) taken a lot more than 180bhp.
It's a good price.
You need to go see it and make a decision based on exterior condition, how it drives, sounds, feels etc.
JJ