No the seats are not the same. The 350/2 seats, the 450 seats and 360 seats are the same and are a narrower version of the seats found in 350/1, 185, 444 and 380. In addition they have armrests and seatback tables.
The seat fabric is not a Siemens inhouse fabric, it is the inhouse fabric of the seat manufacturer Grammer. It is also used on the new HST drivers seats on NXEC and XC fleets (and some if not all GW HSTs) the new seats in 32x and 31x EMUs and additional overhauled locomotives that have gone through Wabtec which invariably use Grammer as their seating supplier.