Likely your house shot. On heavier volumes, it might be pretty outstanding, it was for me at Greater Ozarks. For most, it won't have enough shape on the backend to put up really high scores.
Yes, it is a mental issue that results in physical changes, but most people finish in the same spot. If you end up a foot behind the foul line normally and move up two feet on the approach, you're never going to slide a foot past the foul line. Most people fixate on where they end up at the line, regardless of whether they move forward or backwards, they end up at the same place at the line. I don't think I've ever seen someone move forward or backwards and end up in a different place at the line from where they normally do. It forces them to take bigger or smaller steps to arrive in the same place, and that affects mechanics. You'd screw your head up way too much trying to focus on taking the same steps and then if you end up in different places in relation to the foul line, then your marks have moved, and if your marks move, you're adjusting to get stuff there.
If it didn't affect mechanics, would be no reason to do it because nothing about ball reaction can change unless physical changes are produced.
I hear too many people say they weren't carrying the 10, so they moved 6 inches back on the approach which got the ball to move just enough earlier to get it out, and that's absolutely incorrect. Moving back 6 inches doesn't magically make a 40 foot pattern 39 feet 6 inches.
Well it also depends on what you think changed. The Trick is also not a great house shot ball but yes, will most likely be best on a house shot polished because that will give you more shape. The only thing moving back changes is your mechanics. The lane transition also may have finally gotten to a good spot for you. Most people when they say they moved back or forward think that has something to do with making the ball hook earlier or later. Regardless of where you stand, if a pattern is 40' long, it will stay 40' long no matter how far forward or backward you move . . moving forward and backward changes the length of your steps, which can cause you to walk slower or faster, which changes the rest of your mechanics.
Two things I disagree with.
1. It may be our house shot, but the Trick is an excellent house shot ball - at box finish. A few of use around here have had great success on our house shot with the ball.
2. The forward/backward thing is not true for everyone. While some may see their steps change in length while moving forward/back, others do not. If you don't focus on the change from the foul line, and walk your normal steps, you should not be finishing in the same spot. That's a mental issue.