Slack line needs to be controlled by the glider pilot, varying methods apply. Match tow direction, match tow speed, use drag devices (yaw, spoilers) as needed. Do not over run the tow plane and do not get entangled in the rope. If you chose to release make sure you are not in a position to get smacked by the tow ring.

The idea is a slow reduction of the slack loop, need to match the tow plane speed and he is now accelerating without the glider drag, adding to the problem.

Not all gliders have nose tow or tost connections. Can't always rely on the rope pulling the nose sideways to buffer the tension in the rope.
Why put a side load on a Schweizer style hook. Slack coming out slow, ok. Line coming out fast, not so good. That tension and shock of the line becoming taught should go down the longitudinal axis of the glider, plus the tension has a bungee effect with most ropes. Schweizer gliders with the hook on the chin will pull the nose up.

CG hooks and additional issues. Most pilots will graduate to single seat gliders with no instructor to help. Train for the single seat glass. First learned is what is remembered in a panic. Large slack loops on CG, it could back release from the rope drag, are you in a position to not get smacked by the ring?

Nose pointed away from the tow plane when it comes tight, you can't match tow speed and direction that way, and when the line comes tight the rope has to move the whole glider sideways "through the yaw", not just nose tension.. Greater chance of a rope break, and with increased tension the glider will accelerate in the direction it is pointing. Not pointing towards tow? You're headed off accelerating on a tangent to the direction of tow.

Big problem I have with students and a slack line, normally the glider is out of position off to the side and they want to get back behind the tow plane. Now the big loop is below the nose where they cannot see it or judge how quickly the loop is shrinking if at all. How are you to manage that?

I had one student get us into a bad situation in a hurry with a naturally created slack line in turbulence in a turn. Not instructor induced.
My recovery was "MY GLIDER!", turned inside the turn, got a wing up over the loop, with a big loop I could see going horizontal back to the tow plane.
Pull the release and tighten the turn away from tow. The line and ring goes away from us and does not snap back towards us.

Bottom line, I vote for controlling the loop and slow recovery, don't rush it. Match the direction and speed of tow as it comes out. Cannot always rely on yaw, nose hooks, to control the bungee effect. Can't match speed if you are pointed away from tow. Keep the rope where you can see it. If it goes bad in a hurry, control when you decide to release so you don't get smacked by the ring.

BillT