Take Aim and Think don't need to initialize pursuit when you use them in range, cause they're long distance anyway.
When pursuing someone/something, you gain a slight speed buff for as long as you pursue. If you're attacking someone in melee range, and the pursuit doesn't trigger, they can just walk away from you.
You could argue that this increases the skill ceiling in pvp, but PING exists, so players with higher ping will simply suffer even more from this. but we can still force the pursuit after melee moves in custom clients.
Custom clients will just make it so you also trigger the pursuit after any offensive move besides Take Aim and Think.
The change is good for Take Aim and Think, but it's useless (and makes the vanilla client worse) for all other moves.
Even if you fight an animal and it starts fleeing, you lose some distance just cause you don't auto-pursue it. This isn't a pvp-only issue.