Characters who do melee combat already have to stop themselves from moving after an enemy flees, otherwise they lose the rest of their attacks in that round. More importantly, they might trigger attacks of opportunity from other nearby enemies, since the game decides at random whether your character gives chase or attacks a random nearby enemy.
Honestly, it's a basic part of melee combat. If someone wants to play a dwarven defender, they probably love being right in the thick of it already, and they're used to the game's natural jank. Choosing to chase that enemy and break your stance so you can actually get them seems fine to me, glitching out and moonwalking seems like 2002 spaghetti.
On the other hand, reducing the defender's movement speed to 12.5% while in the stance accomplishes the same thing. They're not catching anyone like that, they're not glitching out either. Right now it seems like a huge detriment to an otherwise rare but iconic PRC.