The seat angle is 77°, which is steep compared to a lot of bikes.
The picture is skewed as the back wheel is propped up but with the seat fully zoomed out, the wheel in relation to the centre of the seatpost is also more forward than most bikes. If you look why its at that angle, see the crank centre and how much to the rear that it has been set.
The small and med also have a 27.5 rear and different length swing arm to the L and XL which are 29" front and back.
S & M 77°
L 78°
XL 79°.
I have had a few bikes with a slack seat tube angle and being a medium, its doesnt make any difference. Now if you were a regular rotorburn giant on an XL with a slack seat angle, the longer the post, the further back you go over the rear wheel while seated. So slack seat angles for small and medium bikes doesn't really matter.
Wheel position in relation to seat centre on a couple of my old bikes with slack seat angles.
The seat collar centre is nearly in line with the crank centre.
View attachment 397536