There are 2 threads going on this subject. The other one points out, correctly in my opinion, that the difference in readings is the setup.
You probably already know by now the camber is the side to side tilt of the wheel. A measuring device is attached to the wheel to measure the amount of tilt the wheel has. I believe that attaching these devices consistently from one setup to another is
very difficult to keep within 1 or 2 degrees.
On the subject of wheel alignment:
The service manual points out specifically that the vehicle level (side to side) at the front and rear axels must be within specification before a wheel alignment is performed (Section 2-8).
The car must be level from one side to the other, otherwise the tilt of the car will tilt the wheels (like parking sideways on a hill).
To perform a wheel alignment, the car is driven onto plates (part of the wheel alignment machine), and the plates are then unlocked, or allowed to slide sideways. This allows the bottom of the tire (the tire patch) to slide in or out, whatever is needed to come to rest. This affects the tilt (camber) of the wheels. Because the car is heavy the plates will slide easier, or not so easy. Especially in the last 1 or 2 degrees.
The rear camber on the CF is not adjustable, and if yours hasn't been wrecked, or seriously damaged, it's likely within specification.
Rear camber has the greatest affect on tire wear, if it's tilted outward, the outside of the tire will wear faster than the inside (reducing the number of miles you get from the tire). Experience has shown me that it takes a significant amount of camber to cause significant wear (more like 10 degrees).
I recommend having your tire shop keep an eye on all your tire's wear (front and rear). If there is uneven wear on the tires, you might decide to peruse the alignment issue. If your wheel alignment (camber and toe) are ok, and you swap the tires side to side every 10,000 miles or so the effects of normal camber and toe won't ever show up on the tires.
I would never try to discourage someone from keeping their vehicle properly aligned and adjusted in any manner, in fact I'm quite impressed with your pursuit of this issue. But, and only a tiny one, it's easy to get bogged down with the specifications. Specifications, IMO, are generated so that we can keep the device performing within the range intended by the design engineer (you might have guessed that I'm an engineer by now).
Wheel alignment is important, especially when it comes to tire wear.