I think the "video game" style walk youre talking about came about due to restrictions such as low frame count, and not wanting to extend legs fully forward or backwards because doing so would require more sprites (old game sprites were actually a number of smaller peices put together).
The arms in the edit arent too long.
And yes, I think by mirroring he meant more about the fluidity of the motions. ie, the arm and leg swing in a similar cycle (though in opposite directions). I think its just that your arm motions arent fluid enough.
the edit is more of a run, yours seems like more of a jog, but you can still adapt the advice into a jog instead.
