Just perusing the spec sheet of the EX540, I don't see any third party safety organizations listing its CAT IV ratings, like TUV, CSA, or UL. Its just the self-attesting CE rating, which is not worth much.
For the money its sold for, $US270-300, the AC electrical specs are no better than low cost DMMs, so most of the money goes into the wireless data transmission and ruggedness, compared to the U1252a, which I own [ I think B vs A is just the color but its electrically identical]. For a few dollars more you can get a DMM with a much more solid reputation, and the 1252a was recently discounted in the US for $140.
Although basic DC spec is a defacto standard for comparing DMM accuracy as DC is more common to use, the true RMS AC accuracy is more difficult to implement and where most DMMs suffer. It takes a lot of effort to get TRMS in the 0.5% range through to 1kHz or even 100kHz.