Context on the Draven Spinning Axe changes on PBE?

Draven: "Spinning Axe (Q) bonus damage changed to [flat 30/35/40/45/50 damage + 65/75/85/95/105% of bonus AD] from [45/55/65/75/85% of total AD]"

I hope that a Rioter from the balance team could give some context to these changes. I'm not complaining, I trust the balance team, I just don't understand the goal behind them and why the sudden changes, i.e if it's a buff/nerf/adjustment/quality of life change, etc.