@Denti
As listed in the UK's BGA's laws and rules: Part 9 - Signals
Page 3 of the Part 9 pdf file dealing with signals controlling a winch launch
"RP11: If the glider is being launched too fast, the pilot should yaw the glider from side to side with the rudder"
https://www.gliding.co.uk/bgainfo/lawsandrules.htm
Pilots are warned during training that before doing this they should ensure that they have 'unloaded the glider' by reducing the amount of back pressure they have on the stick if they are pulling back very hard at this point.
There is no radio communication that I have ever seen used between the glider and the winch during the launch. The only radio communication used is between between the launch point and the winch during the setting up of and the inititiation of the launch.