how Switch DP3T On-On-On work ? Answered

I hope this is self explanatory for you.
Pic2 is a DPDT Double Pole  Double Throw Knife Switch.
Pic1 is a single stack rotary switch and could be as large
as a 12 Throw 1Pole or a 3 Throw 3 Pole or a 2 Throw 4 Pole.
Pic3 is a stack of rotary gangs with the rotary shaft.  .  .  .  .  A

It's true - why do you doubt it?!

0 (blue) = A/B0
1 (blue) = A/B1
2 (blue) = A/B2
3 (blue) = A/B1

L

In position1 the common contacts (A0 and B0) contact A1 and B1, respectively. When the switch is moved to the second position, the common contacts A0 and B0 contact A2 and B2 instead, and so on for position 3.

The diagram appears correct.