This is something that annoys many of us in the trade that know about this stuff.
The way in which the load capacity is measured and, more importantly, marketed to people is in the number of kilograms of laundry that the manufacturer can stuff into the washing machine.
To our mind (the people it annoys) it should not be possible to have these differences in actual drum volume yet still have the same load capacity published where there can be a 10% or more difference. That is not right in our book and in many other industries a practice like that would be abolished pretty smartly.
Can you imagine a one supermarket being allowed to have a 10% difference on a liter of milk over another? Or a car manufacturer allowed to have that sort of disparity over another in its MPG rating?
Either practice would be outlawed across the EU in a heartbeat, as it would get public attention.
Here it does not.
The reason it doesn't is that people cannot actually measure the drum volume so you take it on faith that the manufacturer is telling you the truth or simply made a mistake in their calculation.
It is also the case that, when you ask people what a kilo of clothes looks like or, what it equates to when loading a washing machine, they haven't got a clue.
When buying a new washing machine people will look in the drum and state that it looks huge a just believe the claims being made. But, as the evidence shows, what is being claimed isn't always the actuality, the kilo rating is just some flaky figure given by the marketing people that doesn't really tell you much, as you can plainly see. It also allows the figures to be, we will be polite and say, fudged.
Getting a drum volume is far, far more accurate than a rating in kilograms that nobody understands or can measure.