You can go onto retail right now and confirm leeway exists in 30 seconds. Get a friend, have them stand against a wall while dueling you. Attack them from max range and then have them start running against the wall while you strafe back and forth and your melee range will increase.
Here’s an example I found on youtube:
https://youtu.be/c3rz7opz85E?t=18
Spell or ability leeway also exists on Modern WoW (video creator mistakenly calls it melee leeway in this video: