That model of GE (the lead unit) had the "older type" of GE control stand which had only a reverse lever and a throttle lever. The throttle did double duty as a throttle lever and dynamic brake lever. The reverse lever had five positions, L to R: dynamic in reverse, power in reverse, neutral, power in forward, and power in dynamic brake. To change from power to dynamic braking, it was necessary to lift the reverser lever slightly and push (or pull) it one notch further, at which point it dropped further down than when in power. Doing this changed the electrical system from power to dynamic, engaged the field control rheostat, and disengaged the power starwheel so there were no throttle notches.

The story I heard, from someone who worked out of SPBI, is that the clerk was about to go into engine service and may have been running the engines. This is of course speculation, but it does make a bit of sense with regard to the dynamics not functioning.

On those AAR stands, not only do the handles operate in different directions, the dynamic brake handle is oval, and the throttle handle is round.

The engines in this era of GE had a different firing order than the current ones. At one point GE raised the RPMs of the C-B engines to increase HP output, but they started throwing rods out the side of the block (had something to do with the stresses on the toggle joint). The fix was changing the firing order.