Interrupt Pin Question/Confusion

I have seen some confusion over the pinouts of the Mega2560 interrupts, well I'm confused about some of the documentation.

This site shows digital pin 21 = INT0 Mega2560

This site shows digital pin 2 = INT0 Mega2560

https://www.arduino.cc/en/Main/arduinoBoardMega

This site shows digital pin 2 = INT0 Mega2560

Am I seeing this incorrectly?

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