That depends on the company and the distributor. If they can ship the albums out in shorter time the numbers will be higher. It has nothing to do with the group itself. Hybe is generally great at shipping out stuff and has probably gotten much better in recent times. Sometimes there can be delays due to various reasons and the albums get shipped slowly on first day but catch up later on.

For eg, if FTS got 2M pre-orders , they can ship all of them in first few days or they can ship them over a time period of 1 week. This time they we're able to ship all 4M copies in less than 48 hours. It has nothing to do with the group itself but more to do with the companies that are shipping the albums and the available stock.