I just noticed that your post received no replies, so here goes. I'm not a big fan of this "front arm extension" business. Right off the bat, I can't find any examples in all of my videos of MLB pitchers. I know Tom House recommends throwing the glove out and then bringing the chest to it. Again, what professional examples are there? If anyone out there has any video that shows examples, please send them to "email@example.com". I'd love to be proven wrong here if it results in some truths being uncovered.
What I see is in pro after pro is the forearm and glove pointing toward the 3rd base line during the stride. The elbow comes up to shoulder height, across the front and back/down to the hip during shoulder rotation. Pointing the glove at the target might happen for a fleeting instant as the elbow crosses back and down but it's not an active ingredient here. It would be very incidental. The glove side thumb is pointing roughly downward, keeping the humerus in internal rotation until shoulder rotation begins, combatting early opening.
The problem I've seen with the "front arm extension" or pointing the glove at the target idea is that kids will often externally rotate the humerus very early, facilitating early shoulder opening on the front side and also kids have a tendency to drop the glove straight down from that extended position (you now have a weight out at the end of a lever arm, creating a moment to be resisted), further adding to the front side early opening issue.
So, my personal opinion on this is that I wouldn't teach this front arm extension at all. Study the pros. You'll find very few, if any, who point the glove at the target.