Dear riot... Why do skins not come out when they're supposed to.

If my memory serves correctly, your general releases were spaced by 2 weeks, normally occurring on a tuesday, correct? that hasn't necessarily changed all that much, but it seems that skins always get affected by this. for instance, a while back when the new irelia and talon skins were supposed to come out, they didn't, and despite the patch notes stating that they would come out later in the patch, it instead took a whole other patch before they released, as opposed to releasing alongside high noon. im not sure if this was intentional to begin with, or if the skins needed another 2 weeks for improvement, but its popped up a lot (most recently with the coven skins) where skins either release later in the patch for some reason, or even a whole other patch after that. im sincerely just curious as to why this happens. if i have any information wrong please tell me!