asks "Can someone explain why one would put 2000cs bumpers on and tout it as if it is some sort of upgrade?" Wow. Really? If there's one thing we all should've realized by now on this forum it's that there is room for everyone's personal preferences on these cars. You're certainly entitled to your opinion and I know there is a strong propensity towards originality on the forum but perhaps you'd look at them more favorably if they were described as chrome plated CSL bumpers? (The black fiberglass rear CSL bumper is the same shape as the 2000 CS rear.)
Just to be clear, that is not a 2000 CS front bumper. The nose of a 2000 CS is completely different than a 3.0 and the bumper will not fit. Like the BAT car, the 2000 CS bumper is also all chrome but had its own chrome overriders with rubber strips so the BAT car really is more of a "chromed CSL" look than a 2000 CS look. I don't care for how the BAT car just removed the overriders and exposed the section lines and hardware on the front bumper. Regardless, I'm a huge fan of the BAT car's overall clean bumper look and, since you asked, I'll tell you why...
IMHO, the rubber strips and overriders/under riders are just concessions government regulations, practicality, or poor driving habits. The fact that the original rear design of the car (2000 CS) had a simple all chrome rear bumper shows that this was the designer's original intent. So often good designs are compromised by well-meaning nannies. I think this is a prime example. Clean and simple is what the car deserves when not needing to be concerned about parallel parking mishaps.
One of the reasons old cars please us is the "vintage" look with shiny bits in places that regulation has prevented modern cars from wearing. Bumpers are a major part of this appeal. A clean, simple chrome bumper gives a great look that no plastic bumper cover can hope to achieve.
I don't drive by braille so have no need for curb feelers or rubber bumpers. Of course, I say that with all due respect for those who prefer otherwise. There's nothing wrong with the stock bumpers. We're acclimated to the look, the overriders elongate the nose a bit and have a pleasing rakish angle to them, and the rear under riders serve to break up the flat, otherwise shapeless rear panel. And they're certainly more practical if you bump up against the garage door or the CSL next to you on the lawn at the local Concours.
Some of us like to apply subtle custom touches to our cars, while others prefer originality at all costs. But we almost all make some non-original changes to our cars, whether it be a 3.5 L motor, a 5 speed, US side marker deletion, smaller Euro-style turn signal lenses, or tucking in USA 5 mph bumpers to Euro spec. Most people consider eliminating those government-mandated changes as an improvement. Why not removing the rubber from the bumpers also? Just because they didn't do that in Europe?
I suspect that if BMW had never fitted the rubber strips and over/under riders to the original cars and had instead stuck with a look similar to the car in question, you'd be as aghast by the rogue owner who stuck rubber strips and bumperettes to his otherwise all-BMW example as you are by the guy who walks through Pep-Boys and puts all manner of stick-on fake port hole trim and door ding strips onto his Celica.
Regardless of your preferences, I certainly respect your right to do with your car what makes you happy.