A little thought experiment.
1. Remove the reverser buckets, attached chains to the rear engine nacelle, and stand in the exhaust flow holding the chains. You are now the reverser plate/bucket.
(yeah, yeah, assume a heat-proof suit!)
2. Run the engine up - will there be a substantial force pushing you backwards, and straining both your arms and the linkage chains? And by way of the chains, pulling backwards on the nacelle?
Y or N?
The force on your body is a measurement taken outside the frame of reference of the aircraft. That will result in erroneous results when viewed from the frame of reference of the aircraft.
In experiment #2 while your body is experiencing much more "negative" thrust you are neglecting to account for the higher "positive" thrust produced by the engine.