They could be leather now as they've been available in leather OE in GT's since about 2013.
I haven't looked in a while.
When I got them, 4-5 years ago, they were only available like this. Exact copy of the Boss seats.
Material with alcantra inserts. Better for holding you in anyway. No sliding on leather.
I think they were like $2800.00 US at the time. I got free shipping on them.
Pricy but great investment. Drop weight too. Noticeably lighter than EO seats.