I don't think that that's what it means.
Going from 240v AC to 120v AC will only make the efficiency of the power supply drop by 1 or 2%.
Assuming the GUI is reasonably accurate, then at those settings your power supply is 82% efficient (134.5 / 164 = 0.82).
Most modern day power supplies are closer to 90% efficient. So I'd say on the DC side of the power supply it's probably closer to 145 to 150 watts.
As you say: I interpret this different.
The label clearly says:
"85-176VAC Load power 60%"
I read this as : with input voltage 85-176 Volt AC the load power should be limited to max 60%
I don't see anything that says 1-2% less efficient on that label like you interpret it.
The WEB GUI uses the amps/volts of the VR x 3 strings to calculate the ASIC power usage.
Then it adds a guessed amount for the ESP32 & the fans to come to a WEB GUI power usage number.
It is not 100% measured.