[SkinnyG]

I've never heard it called an economy valve, but your understanding of how it works is reasonable.

One of the ways I describe it all is this:

You want a good, perfect idle, so you make the idle fuel ports adjustable with mixture screws so you can make it perfect.

You want good full throttle power, so you make the main jets big enough to feed the engine for full power.

Except that will be too much fuel for good economy when cruising, so we create a valve that can restrict most of that fuel for when you're cruising. On your Holley, it's a Power Valve. On a Q-Jet, it's the metering rods and power piston spring.
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Curious - what is your idle vacuum reading? It is often recommended to have the power valve open at half your idle vacuum reading.