Yes it is correct. Your skins appearance, not just about weight loss, is largely about your genetics, of course you can support your skin health with a good diet, good collagen levels, make sure you are not deficient in anything, moisturising to avoid dryness, but ultimately if your skin has been stretched for 40 years and you do not have natural skin elasticity, you're going to have loose skin, whether you lose at 2lb a week or 5lb a week.
You would see it more starkly with a quick loss, which is why its said that its about rapidity, imagine your body changing so significantly in such a short space of time, you're unrecognisable. But if you have loose skin suddenly its right there in front of you. If you lose that same weight over 2 years, that appearance isnt so shocking
When people have WLS, they dont all experience loose skin even if their journeys have been similar, ie someone losing 5 stone over 5 months perhaps could have lots of loose skin and a person losing the same in the same timescale wont.
Black people in particular rarely have loose skin from weight loss statistically.
In any case, the reality is, WLI dont result in 'fast' weight loss, they usually centre around 1lb or 2lb a week loss which is perfectly reasonable.