From what I somewhat understand, it locks your FR somehow so you can change tunings, then you take it off and your FR is still in the same tension as before...?
This post may contain my opinion and/or inaccurate information.

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No, it basically makes the tremolo unusable, by making it completely inanimate. It pretty much makes it into a hard-tail. You always have to adjust the tension if you want to use the tremolo, no shortcuts.
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I'm pretty sure it is just made to where you turn the screws and it makes it to where you can have it locked. I think its kinda like having a tension spring that you can adjust on the fly sorta also.
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It has different settings. You can make it passive to where it doesn't do anything and the bridge moves both ways. You can make it to where the bridge won't move up or down. Lastly, you can make it to where the bridge will only rise.

It comes with a special claw so you have to take out the one in your guitar and solder/attach your grounding wire to it, put the springs back on and that's it.

But yeah you can tune down without changing the tension, but the thing is if you're going to want to use baritone tunings you may not want to do that because it's still going to be putting a lot of tension on the Tremol-No.