PO Choro & Seamaster Chrono - Why both?

Just reading this article on Monochrome.
OMEGA SEAMASTER DIVER 300M CHRONOGRAPH MASTER-CHRONOMETER
It's really good and goes into the history of the Seamaster chrono.

After reading and really enjoying the idea of the SMC Chrono it made me think about the PO Chrono I waned.
I can understand the PO and Seamaster both existing. The PO 45mm vs a Seamaster 300 are two completely different watches but to have the PO line and the Seamaster line with so so so many variations of both.

Made me think... Why?

There is a wrist shot from right now. Just for viewing pleasure.

Not sure I understand? I don't think that any current Omega watch is not considered a chronometer by one standard or another.

Tom