Since 5.13 (long time ago now) slow doesn't stack anymore, and the highest slow is the one applied. Old Rylai's passive specifically said it slowed, but the new passive on PBE says it 'reduces movement speed' - does this mean that it stacks with slow effects? And does it stack with itself? Regardless I find it an odd choice of wording. I'd ask on the PBE boards, but I don't have access.
Can you post the PBE patch notes link so that we can see what you are referring to?
It's the same deal, the tooltip will be fixed eventually.
What they need to do to the item though is not let every tic of a DOT spell re-apply the slow. Part of the reason champions like Malzahar and Brand are so busted is because Crystal Scepter perma-slows you for however long the DOT lasts for (For Malz it also procts off of EVERY VOIDLING AUTOATTACK). If they removed this interaction then the item would be so much more balanced.
