CB, sharp eye!
These are the dangers of coming back to a long neglected project 
. I started the development on 2313 for one stepper and later switched to 328P to do all three on one MCU - 2313 did not have enough I/O. Fast forward 8 months and I forgot which MCU is plugged in there (and the names of the sketches corresponding to the MCUs).
Feel like an idiot, really. But, thanks to you, the mystery is solved!
Cheers!