Testing spread without reflective walls would be beneficial for anybody with a larger size grow. Large canopies don't have the luxury of having much/any wall reflectivity.
Reflectivity will skew stand alone results.
Just think larger than a tent.
Nope, when you have a large room, reflectors are most definitely useless. At 30cm above the canopy, the COBs have a spread of around a meter. So a COB more than 50 cm away from the wall should never have a reflector. The bit of light that falls outside the beam angle will bounce back just as well on the wall instead of a reflector. As shown by Malocan. Even with a less than optimal reflective surface.
Besides, if you would want to measure the footprint of a COB for a large grow room, you should include all the light and not just the portion of light in the center. Preferably a COB should then be placed in the middle of a 4'x4' area and then measure the whole surface like Malocan did.
Either way, this is no longer a theoretical discussion. You can clearly see in Malocan's data that over the whole surface the bare COBs end up with 20% more light on the plants. Therefore, smaller or bigger room won't make a difference. Reflectors clearly always lose a lot of light.
Reflectors only make a tiny bit of sense when you insist on hanging the COBs higher than needed above the plants or if you insist on not having walls at all. Even then only on the outer COBs and only if you replace the reflectors every grow or maybe every two grows.