Another hype...
I see... it seems to be a trend nowadays with most (or all) manufacturers to push their machines to the limit in their relentless struggle to baffle the public... astonishingly even Miele have done this with some of their recent models... but to a smaller extent.
It is, in a way, the same principle as… you've probably seen on a different thread which has been opened here recently about a machine with a 12 minute wash cycle: the primary purpose of cleaning laundry is somewhat served…
A 62 litre drum will probably accommodate 9kgs of non bulky items (thrusted in forcibly... but not towels please) and wash them sufficiently given the prolonged cycle times, provided that they are lightly/normally soiled...
Likewise... a 12 minute wash cycle will wet the laundry sufficiently (if meant for a petit load) to make it appear... rather damp at the end... well, given the short duration of the spin cycle too), however, all this becomes inflated and amplified by the media through advertising and marketing techniques.
I have noticed the difference in drum volume between my recent 6 kg Hoover and my parents’ old 6 kg washer: the Hoover has a visibly smaller drum... but the difference doesn't seem huge... I haven't measured them but I will one day

Although, I tend to accept this situation cos' I can still load the washer to near enough its capacity obtaining more than reasonable results (using long cycles), yet, it's enough to go above its declared capacity by a few hundred grams of laundry to see all the typical symptoms of an overloaded appliance!
In your case… having to load the machine 2kgs under its declared capacity seems a bit extreme… although 7kgs of laundry is quite a bulk… and… as Matt suggested, even 6kg of laundry is more than we might first think... well… I’ll second that… and I’m sure my dryer and my clothes airers would too!