Well. It make sence SOMETIMES to pass short when the order is long,
BUT in many cases these short passes has NO CHANCE to get a new First down and are WORTHLESS even if "succeed",
while the ORDERED Medium/Long pass would have SOME chance even to a player with defender close...

The sim now and then DO try long/medium passes to players COVERED by MORE than one defender, some times even 3-4 defenders there, when it ISN'T necesary.
So why don't it try to pass to a player with defender close, when I have ORDERED it to when it's necesary...? :)

It's a bug - or something wrong in the logic.
Some CAN'T be dumps in plays ment to be long/medium.
I suppouse we agree that RUN plays are SHORT (?)

Here is one example:
Gameplan set to ZERO total for 3rd for such distance for outside run, inside run and short passes, but it make a run anyway...
https://mfn48.myfootballnow.com/watch/5176#916053

I just looked at your gameplan, and noticed that your gameplan adjustment speed is set fairly high. The previous play was for 30 yards (even though it was a penalty and called back, it is still used to update your averages). This moved 3rd and 16 to medium instead of long, which restored the running plays. You might want to return the adjustment speed back down to the recommended values.

Remember, the adjustment speed is the weight applied to the most recent play when updating your distance expectations. An adjustment speed of 100 after that play would have made 3rd and anything less than 30 to be short, because the algorithm assumes that every play would be 30 yards. You didn't have it set to 100, but it was high enough that the 30-yard play would have easily made 3rd and 16 as 'medium' for the next play even if you had a previous average of zero.

I haven't updated the blog in a while, but this article still applies as to how short, medium, and long work: http://blog.myfootballnow.com/2015/03/short-medium-and-long-what-do-they.html