Battery drain issue

Not weird. The one with the grounded field brush is for 69/ earlier, the other is 70/ later, and then "long about" 73 or so, they went to the "squareback" which is an improved design

Plain and simple the parts guy screwed you
Looking at the pictures (I pick it up tomorrow) the square back field terminals are located a bit different than the alt I’m replacing. Does it matter which wire goes to which field post? Those wires are green and blue on my car. The blue was closest to the main battery wire on the old one.