IMO, there should be forward pressure put on the bow from the bow arm. It should be directed straight with other alignment points.
The tough part as mentioned is to keep it consistant, but it needs to be there. Fortunately for me it is an aspect that is pretty much ingrained in my shooting, so I don't really think about it often. But some do, especially if they use a more static, arm up before draw type of form. Personally, I use a swing draw, which incorporates this aspect.
Below is a link to a shot Howard Hill took, it is looped, so you can watch it a bunch of times. Look at his forward extension and tell me it's wrong.

. But I have also seen clips of him shooting where is not as pronounced.
HH-Loop