I had emailed this question this morning, and got the invite from Evan at Adtran.
This afternoon I had an FST dispatched to TS the DBU.
I think my field services tech figured it out. The lights and labels are located on the same line, with the lights to the left. As English goes left-to-right, my FST looked for "DBU" and then looked at the light to the right of it. That is actually the switch port 1 light showing link up and regular traffic. There is extra spacing between the switch ports, but the spacing between the STAT, WAN, VPN, DBU, is very small... and it is this small interval between DBU and switch port 1 as well.
TL;DR, DBU light is to the left of DBU label, but users and techs are looking to the right of the label and therefore reading the wrong light. LIGHT LEFT!