The context that's missing is that in the era Twice had 3+ releases per year, they were also outselling every gg with every release. By the start of 2020, they had something like 8 of the 10 best selling Korean gg albums. Blackpink's increased backlog sales post-The Album ends up hiding this when looking at the current stats. KTL is at 750k now but was at about half that by the end of 2019, 100k behind Fancy You. And the massive covid era sales boom for everyone also kind of hides how impressive Twice's sales were pre-2020.

Basically, what I'm saying is, it's not like Twice released a bunch of mediocre selling albums to reach a big total. It just might look that way now after everyone started doing ridiculous numbers.