Does moving affect ADS reticle accuracy?

In short: Do bullets land where your ADS reticle aims at the moment of firing, even when moving? Ignoring bullet drop here.

I initially was under the impression that bullets do land exactly where your ADS reticle is aiming at, even when crouching, during leaning or walking. The amount of bounce/sway might be more than when standing still, but if you aim your reticle at a head while moving, and you shoot, it should be a headshot.

However, I've been noticing (especially with the K2) that bullets sometimes land quite far off to the left or right of where I am aiming and I'm trying to find an explanation for this.

Example (although poorly edited)

https://www.youtube.com/watch?v=HhwiPByrMkw

The first three bullets hit next to the person (landing on the boxes), even though the reticle is aiming on the person.