Sound wrong to me.

It's a digital stream, and channels will be scattered all over the spectrum. You basically want a meter to read as close to 0db as possible at any outlet, regardless of what you're plugging in, or what the content is. Unless the HD receiver for whatever reason has a much weaker tuner than the SD receiver, or is at the end of a much longer run than any of the others, but even then the premise is wrong.

So long as the meter is showing the target signal strength, whatever he plugs in - in whatever order - should work fine.