How many I2C lines does the Arduino Due have?
According to the Wire library documentation https://forum.arduino.cc/index.php?topic=132130.0:


  The Arduino Due has two I2C / TWI interfaces SDA1 and SCL1 are near to
  the AREF pin and the additional one is on pins 20 and 21.


And the table:

Arduino Due: 20 (SDA), 21 (SCL), SDA1, SCL1

So it seems in your table SCL2 should be SCL1.