It appears BxU has mostly fallen out of mainstream use, at least in public-facing lens tests. The only clear example mentioned here is SLRGear, which publishes “blur units” or a “blur index,” and those seem to correspond to DxO’s BxU concept.

In general, lens testing today is more commonly reported with standard MTF-based metrics because they’re widely understood and comparable across tools and labs. A proprietary metric like BxU is harder for others to adopt if the underlying method is not fully disclosed.

So the best conclusion from the provided information is: BxU is not widely used, but the idea survives in at least some blur-unit style reporting rather than as a broadly adopted industry standard.