I'm curious as to what vendor Apple is using for their 512g and 1Tb SSD's.
What does that have to do with anything? It can still be based on the 960 just with a different connector.
I expect them to be "Apple" brand. Some years ago, Apple bought an SSD controller company. Thus it makes little sense to pay for someone else's controllers.
As to who makes the actual SSD chips, ... I don't know.
They are Samsung drives. Apple doesn't actually make any SSD's themselves, even if they may help design them.
My 2TB gets reported as
Model: APPLE SSD SM2048L