That little thing that sticks through the back of the Steel Will cutjack when closed is not a thumb nub but rather a flipper tab which allows for easy opening of the knife with the index finger.
Once open it also flips down and acts as a finger guard protecting your fingers against sliding up on the blade.
I can’t recommend the steel will cutjack enough. It is a great knife.
Also you could check out the Spectrum Energetics utilizer. That way you can have a nice knife and if you accidentally bring it to the airport you can just take the blade out and throw the blade in the garbage.
Spectrum Energetics Utilizer.
In my Experience the SoG folders are not great knives that often have blade play. Which means the blade wobbles around while locked open.