SERVO0_PIN is the complete difference.
Marlins pins_RAMPS_13.h used to use the 11 what is correct for RAMPS 1.4 but not 1.3.
Please compare [reprap.org] with [reprap.org]
And if you don't trust the legend, as i did, follow the tracks in [reprap.org] and [reprap.org]
This shows a light on how many 1.3 boards are out there, in the wild.
Marlins pins_RAMPS_13.h used to use the 11 what is correct for RAMPS 1.4 but not 1.3.
Please compare [reprap.org] with [reprap.org]
And if you don't trust the legend, as i did, follow the tracks in [reprap.org] and [reprap.org]
This shows a light on how many 1.3 boards are out there, in the wild.