OP, your thread is titled, "Can they fire your for OVER production"? Well, not sure why you asked this but in your case, coming in early falls into that somewhat. Maybe they already have you on their radar...they know you start early....it would be their ace in the hole if they want to discipline you.
Don't think by them not saying anything that they are oblivious to the situation.
Quick dirty calculation is at $10 per hour, your 10 min comes out to about $500 per year. So at Christmas you gave them about 2 paychecks to come in early. Instead of going out and getting something for yourself.
I can't think of any preloader...anyone for that matter, who would work here for almost 2 weeks without wanting a paycheck.
It all adds up.
Only for them to tell you to "hurry up" or "pick up the pace".
That's one reason we are leaning on you hard to stop working off the clock.