Here's another vote for Uplula. I have two of the model sold for 9mm to .45ACP. They also work on my 380 magazines.
And yes, they also work to unload magazines. The tab on the fixed side will push out rounds faster than you can unload by hand. I use it to unload hollow-points (home self-defense) when I take a mag to the range, since I shoot FMJ for practice.
I have no idea what tab you're talking about, but if it works for you that's great.
....... However, I learned last week at a machine gun shoot, if you are going to be loading dozens of mags over and over, look into getting a Mag Pump Pro magazine loader.....
It's on the instruction card that comes with an Uplula, but here's a short video https://www.youtube.com/watch?v=jBY4tvdHMY8&t=30s
I've had mine for years so I checked the instructions and it made no mention of the unloading procedure. You can learn something new every day. See the photos.
Uplula. Look no further.