So apparently the 'relay' he used is an answer to everything. The way I understand it is that on the wire that goes from bottom to upper part of the seat he fit in a relay that controls voltage and power that is used to heat up the upper part of a seat. That way if there is no signal from climate control to the seat about heating being turned on, the seat remains turned off. And whey signal is sent then a relay is doing its job. If that makes any sense.
and another thing, just today I found out about different solution as well but i have only pictures of the device that was built to do the trick. I don't have any other details apart from that it has been made by some electrician to get heating working on 2013 sline seats from a3. Lovely seats tho.
I can post pictures here if anyone is interested