The buttons were cheep ($5) and I could have went with a unlighted one for much less.
The LED lights on the Raspi board stay on if power is going to the board as does the LED on my USB stick. That doesn't indicated that the pi its self is running.
This button is like typing "sudo poweroff" or "sudo shutdown now" You still have to pull the power cord if you want totally no power to the board. The bonus is the wake up, no need to pull power cord then plug it back in.
Logging into the pi via puTTy then typing "sudo poweroff" seemed like more work then was needed, this even eliminates typing a "sudo reboot".
I noticed the buttons have a small rubber ring (for water seal?) that I'll remove when I add to my CM15A cases. Adding this to my 3B+ case was just a trial run.