nobody in their right mind or half out of it would ever start a
winch launch with a wingtip on the ground.

I expressed that opinion at one club recently and was told, no we do it regularly.

It might not be too dangerous if the winch technique was adjusted to give an initial acceleration to 20 or 30 knots for a couple of seconds before giving it full noise, possibly in response to an "all out" radio call.

But I got the impression they didn't bother with anything like that.

Sorry to contribute to thread drift, but I just have to respond.

Launching with a wing tip down is probably the number 1 "NEVER DO" in winch launching. It only takes a brief snag of the down wingtip and the up wingtip will accelerate and fly over the top. The glider becomes a giant hammer with the cockpit as the hammerhead driven into the ground at high speed. When this happens, it is all over in a couple of seconds and is nearly always fatal. Same thing for dropping a wing on a winch launch. Release immediately if a wingtip drops on a winch launch (Should never happen with a properly driven launch as the very rapid acceleration makes the ailerons effective almost immediately).