Are you changing the source and destination in your tests? Try running tracerout to different destinations multiple times each and change the source addresses also. You should see over a period of time, the changes. It will not be perfect round-robin, but per-flow. this is what contribute to the improvement in applications requiring low latency. When you run the monitor traffic interface, are you not noticing the output packets roughly close over a period of time?
Can you provide the output of these commands ?
> show pfe route ip prefix x.x.x.x/24 detail > show interfaces xe-0/2/0.0 | match rate > show interfaces xe-1/2/0.0 | match rate > monitor interface traffic (just the sections for these two interfaces)
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