I think we have different understandig what nerf is. For me its making unit less powerful. Here You can call nerf only 1 thing. Volks without schrecks (yet still you have something for exchange so its hardly nerf). I would rather say its a buff since you still have at inf and ai cheap inf. But if you are schrecks blob lover, then yes, its a nerf.
Other things are about changing design rather than nerfing.
They are nerfs because they weaken the faction and the units.
If Riflemen came with sticks instead of rifles, but could still upgrade to rifles for 60 munitions, would you not consider that a nerf?