Since 16.1 stone axe has been given -20% quality debuff on mining, while tinker's throwing axe only have -10% debuff along with other bonuses for mining.
I see there's an implication to use it for mining as more viable tool, but to which degree should you not understand your own game to do changes like that?
Any mold item is much more complicated to craft quality-vise, it's going to be nearly impossible to make tinker's axe nearly as close as stone axe could be.
For the entire time being stone axe was the main tool to progress with, as it's the only thing allowing you to receive qualities as close to natural high quality of a stone. As always I think this change hurts avg quality players more than anyone else.