Swiftness only works on walking up/forward..
How are you measuring? +33% to the base movement speed for strafing and backpedaling isn’t going to produce a noticeable difference if you are just eyeballing it.
from point A to B without swiftness (or any other movement increasing) walking back its like 4sec.. with swiftness its still 4 sec, (and if it does work it should be 2,6sec you would see the difference)
If point A to B is 12sec and swiftness should work its 8 sec, that’s allot.
Maby you think, nah its just 4 sec.. but that’s allot in PVP when you often walk back or left/right when using a range weapon.