They didn’t though. She currently has a 30% movement speed reduction while firing, identical to Reinhardt’s penalty from holding up his shield.
D.Va’s movement speed buff while firing is the only one not to go live in its full glory, splitting the difference between the old 50% and the tested 30% with the 40% we have now.
Edit: Ahh, then I guess D.Va’s was the second time. I could have sworn it was just 30%, though…