That is exactly that. 50lbs is the limit in the US, and usually 25kg is in Europe, which is why often airlines will close an eye for up to 1.5kg over (24kg rounded)

The same reason why you can have 2x23 or 3x.23 but you can't show up with 1 pc of 30kg. Premium cabin have 32kg limit which is an extra service (heavy bag) for the handling.