WvW Repair Master doesn't spend the last bit of supply as one unit

[Leablo.2651]

Scenario: I have Repair Master 2 (spend 6 at a time). I am holding 15 supply.

If I go to a damaged wall and repair it, I can see that the first two hits will, as expected, spend 6 supply each, bringing my carried amount to 3. But now it gets strange because instead of spending the last 3 in one hit, it first spends 2, and then the last 1. Incidentally, this makes the interaction take the full length of the interaction bar, so at first I thought this might be caused by the game trying to stretch the interaction to fit the animation. But even if I break off the interaction, to start a new one with 3 supply, it still spends 2, and then 1, and then breaks the interaction (for not having supply).

So what I would expect to happen in my scenario is for the interaction to go 6-6-3 and then break animation. Otherwise it largely defeats the purpose of having this ability since it drags out the interaction time.

[idolin.2831]

Bumping this up because this still exists and is quite annoying.