My measurements in the past have shown the opposite.
The flow of power is from front to rear.
To show visual evidence of this I have done the following.
I soldered three fuses together in series. This gives extra length to both make contact at the front where the fuse makes contact and easy access to measure voltage at the rear.
As you can see I measure 123.3 V at the other end of the fuse. If the flow was from the rear to the front I would expect to measure 0 V at this point.
These pictures are on the Direct Stream Memory transport but I did the same experiment on a P 10 powerplant with the same results.