^^^^Yep
Even with a simple cable pulldown it's not the same as a pullup by any means. With pulldowns you body is not moving through space so you're moving the weight through a fixed plane. Plus you can cheat and use your lower back to get more momentum.
In fact you're getting into open kinetic chain exercises and closed kinetic chain exercises. There are no hard and fast rules because of difficulty of applying load progression to certain closed chain exercises (for example push ups) but in general I can confidently assert that closed chain exercises like squat and pullups may make you much better at open chain ones like pulldowns and leg press, but the open chains don't prepare you anywhere near as much for the closed chain ones.
OOPS, there goes that lab talk
