Agreed. The nerf is clear as the day.
- Sarada was stated to have fairly good amount of chakra in the Boruto DB (even more than Boruto, and he never runs out of chakra, even though he spams his clones).
- Sarada has CES and Genjutsu affinity, in other words, very precise (if not perfect) chakra control
- She stated that she trains her Sharingan
You see, it doesn't make any sense for her to have stamina issues while using her Sharingan. Considering all of the above, Sarada should be able to use her Sharingan perfectly without wasting a single drop of chakra. There is no reason for this other than nerf.
Either nerf OR her Sharingan is waaaay too potent that she can't handle it perfectly just yet.