Human Design has nine centres where the chakra scheme most often cited in modern Western usage has seven. This is one of the two that were added, and it has no classical counterpart at all.
What that means
The Head, Ajna, Throat, Sacral, Solar Plexus and Root all sit where a classical centre sits, whatever differences there may be in what each scheme says about them. The G or Identity centre does not. It is placed in the bodygraph between the throat and the sacral, in territory the classical scheme assigns to the heart centre, but it is not that centre: the bodygraph has a separate Heart already.
The addition is Ra Uru Hu's, published in 1987 along with the rest of the system.
Why the addition matters for reading the system
A borrowed scheme with two extra elements cannot be checked against its source, because the extras have nothing to be checked against. Claims about this centre stand or fall on Human Design's own authority and on nothing older. That is true of much of the system, and it is most obviously true here.
The other addition
The Spleen is the second centre with no classical counterpart. Between them, these two are the clearest evidence that the bodygraph is an adaptation rather than a transmission.
The atlas records Human Design as a contemporary system and not as ancient material.
Sources Rainbow Body: A History of the Western Chakra System from Blavatsky to BrennanKurt Leland with The Human Design SystemRa Uru Hu (Alan Robert Krakower)