Limiting Work In Progress in Kanban --- Effect or Side Effect

I was going through the kanban guide and it says under topic of "Limiting Work in Progress (WIP)" that The primary effect of limiting WIP is that it creates a pull system. It is called a pull system because the team starts work (i.e. pulls) on an item only when clear that it has the capacity to do so. When the WIP drops below the defined limit, that is the signal to start new work. Note this is different from a push system, which demands that work starts on an item whenever it is requested.

Whereas in a blog (https://www.scrum.org/resources/blog/professional-scrum-kanban-psk-dont-just-limit-wip-optimize-it-post-1-3) , it mentions as The primary side effect of limiting WIP is that it creates a "pull system." It is called a pull system because the Scrum Team starts work on an item (i.e. pulls) only when there is a clear signal that it is time to do so (note this is different from a "push" system, which demands that work start on an item whenever it is requested). When the WIP drops below a defined limit, that is the signal to start new work.

The word effect is replaced with side effect. My intention is not to pinpoint the error, but ask the community , is the pull system an effect or side effect in Kanban? Appreciate your views.