That’s the Key .. I owned the Equitech ET2Q for over 20 years.. The secondary winding has a higher output. The unit if fed 120v, will output 124-126 V, half that on each leg. They do this to keep the voltage from sagging under load. So if you lightly load it, you will get a higher voltage, even a medium load will still yield more voltage than the incoming line..
When I removed my BAT mono amps from the system, the unit kept delivering 125+ volts, which was too high for my low powered tube gear.