Currently, the animation comprises 1) a popup tooltip and 2) a vertical colored bar indicating the new target position of the tab.
The tabs are not actually repositioned until you release the mouse button.
(there is also a ghosting effect on the tooltip which I think is a bug)
IMO, the implementation in Brave / Chrome is simpler, easier to track visually, and provides a clearer preview of what will happen.
Here, there is no tooltip or preview marker needed; instead, the entire tab & its title move along with your cursor.
It’s somewhat subjective but I suspect many others will agree.