Yes, I had assumed the same as you but then rethought things based on what others pointed out.
In the carjacking rape Cannan committed, he did make his victim drive somewhere secluded. The car with the victim in it had been parked somewhere quiet when he carjacked her.
SB was very different, possibly because he already knew her, perhaps only as a nodding acquaintance. Carjacking someone in a busy car park would be very risky, raping SB then letting her go would be risky if she knew him and definitely if he had carjacked her and drove her to where he lived - she could literally bring police to his address.
And where did she call in sick from the next morning? Taking a victim to a phone box to do that would have been very risky in broad daylight especially. I'm guessing she called from Cannan's flat (no call tracing back then?). She didn't sound stressed or under duress on the phone.