not sad, it is how DLSS works. There are fixed modes for DLSS and these specify how much DLSS do the down-scale. And DLSS is made as performance reason only.
DL - DLAA is, as mentioned , is a special DL mode where zero down-scale is done and that is for image quality only. The gpu cores are used to make the image with the native resolution even better ( e.g. remove artifacts ). Thus, pretty normal that “under DLSS setting” no scale setting is reachable.
In contrast is DSR an up-scale algorithm to get better image quality. But also here exist in nvidia control fixed values. Therefore the hint that the OP can simulate with that also 4K, but may be better is then render-scale, if not DLSS is active.
The old DLAA have nothing to do with DL DLAA , therefore here the scale setting is still present.
What I not understood: you fly in WQHD setting on your 4K screen , so you set a downscale. Why you then try to DSR, just switch back to render-scale 100 