Vertical Travel Skills cover less distance than when used horizontally, affecting Momentum

So I am using Gathering Storm for clear, and slapped on the Momentum support gem, which adds more damage if you travel 2 meters with the skill. This works fine with Gathering Storm's initial wind-up backstep if I'm using it to the left or right, as I can see my character flash green to indicate the buff is active.

However If you aim this skill vertically, like up or down on your screen, so that your character moves vertically during the windup - Momentum is not triggering during the windup. I can see the green flash appear during the dash at the end, but this could potentially mean that it doesn't trigger until late into the dash, meaning the damage of this skill is inconsistent depending on your map layout, which is a bit frustrating.

The character in general seems to cover less distance with anything vertical, whether it's basic movement or Travel skills.

(The Momentum problem in particular could also be specific to character Movespeed or the Attack Time of the skill so I'll leave mine: Movement Speed Modifer: +31.00% - Attack Time: 1.10s)