A long time since I played at being a tug pilot.... (and I say that with not the slightest flicker of a wry smile on my face)
A glider does its very best to drive the tug and pull it into line with the result that the tug pilot has two options .. either
(a) slip (which I had never thought anyone would permit due to the reduced climb performance ... nobody like a glider pilot to keep an eye on which tug pilot gets to height quickest ... and crucify the pilot who costs him/her an extra dollar or two) or
(b) use the leg to make it fly nicely and properly.
.. or am I just being old fashioned ?