Spindle Control and Limit switch use same pin?

Here: http://blog.inventables.com/2014/06/shapeoko-upgrade-quite-cut-spindle-with.html it says "Wires from gShield to relay. Red is +5VDC, yellow is signal wire from D12, green is ground. "

But in the instructions: http://x-carve-instructions.inventables.com/step14/ the Z axis limit switch is in D12.

What am I supposed to do? Is the spindle supposed to shut off when it reaches the limit?

The instructions from 2014 are referencing GRBL 0.8.

In GRBL 0.9 and later the spindle enable pin was moved to D11.