In older versions of Linuxcnc there was only one touch off button. Then you had to choose the work coordinate system or tool from the sub menu. The newer versions separated the tool part to its own separate button, otherwise functionality is the same.
it was to save people like me from making the mistake of touching off the coordinate system rather than the tool because we forgot to operate the drop-down selector.
I did it so often that I actually asked for the new button.
