I believe the way https://uk.diplo.de/uk-en/02/visa/ai...-visas/2442170 is meant to be read is, that most people can transit from non-Schengen to non-Schengen on airports that have an international transit section. Certain nationals incl. those from Pakistan must have a transit visa, even when their flights wouldn't require to enter Schengen.* This transit visa is not required when you already have a residency in EU/Schengen states. However if you want/need to enter Schengen to make the transit, then you need the visa anyways.
* I assume this list is compiled of countries that are known to have Europe as a popular destination for asylum and they don't want people to use the transit as a way to knock on the door.