Eh, part of a turn, 2 turns...I don't remember. It wasn't much either way. Still, all you were doing at that point was taking up the slack rather than really compressing the spring. If you'd kept on winding you'd probably have found the effort stayed about the same (ignoring the effect of it feeling harder because it's tiring work), or increased at a linear rate. On a progressive spring the effort required increases at a non-linear rate. Think of this: if you were to wind up the spring seat by 1cm while the car was on its wheels, the car rises by 1cm, but the force compressing the spring remains the same because the car hasn't got any heavier - on a graph of force against compression, you're still at the same point.
Many of the more expensive kits also use non-progressive springs - the Bilstein B2 coilovers that I fitted to the wifes car for example - which only adjust ride height by moving the spring seat. Now, I think that Bilstein know more about suspension than I do, so if that approach works for them, it must be OK.