I think it makes more sense in EU than USA and UK.
USA is 120 V, so lower, safer voltages.
UK is primary single phase systems.
EU - in my flat, I have 3 phase (3x230 VAC fixed installation) electric cooker - according to FLUKE it is CAT III, despite IEC61010-1 has other opinion on this topic (FLUKE:
) however, per IEC61010-1 installation efore my electricity meter/incomer fuses is CAT III - hence even for "home use" I may need to measure CAT III line for checking if my fuses are fine. To do it I would need CAT III 300 V meter - quite rare thing - most meters is better than this.
Per FLUKE lighting in staircase is CAT III - again, IEC 61010-1 would rather categorise it at CAT II - definition of "large building" is vague. Anyway, drawing line between Overvoltage categories is tricky.
One more thing, which may affect FLUKE, an USA company: mostly wooden small buildings in USA/UK provide little EM shielding. Buildings in EU are more often reinforced concrete and this provides
some level of shielding, reducing overvoltages from lighting strikes.
Anyway, portable DMM with CAT II only makes indeed little sense, and seems to die out already. For me at least