No, it's just turning. You're confusing 'change of rate of turn' (vs just rate of turn) both of which would definitely reduce as the velocity slows (especially) if the spin axis is only changing 'slightly' or hardly at all, as Erik notes.
for that matter, there's still the impact of the angle the air hits the ball not just on the flat plane, but the ball also goes up and down - picking the best reference frame is even a neat trick. So if the spin angle is constant to the starting point, it's not constant to the changing velocity vector......or vice versa
combine that with the linear velocity slowing down and the shape of flight starts to make sense
it still makes best sense to take the forces on the ball and split them up at right angles to each other - this does not mean there are two spin axis, it means that the single spin axis can broken into component parts
I hated dynamics of motion in college, probably the most painful course ever. This is the kind of stuff we'd see on exams that had to be graded on a curve....(see what I did there?)
I'm full - enjoy the discussion
Edit: I just noted my Icon.....oddly coincidental