> as we all know, the powermac G5 series is a Sata 3gbs aka "Sata II" device.

Official specs say it's SATA 1.5Gbps aka SATA1.

> in some recent testing with my latest G5 2015 2.0

2015?

> port "A" is indeed sata2, whereas port "B" is Sata3 6gbs.

While SATA2 (released 2004) is theoretically possible in a computer from 2005, SATA3 is from 2009 and thus cannot be in it.

> you can boot and use modern sata3 ssd's on port B.

Interesting find. Yet, this doesn't mean it's a SATA3 port (or SATA2 for that matter). SATA protocol family has good backwards compatibility, although usually only one generation back, so SATA3 devices usually work in SATA2 ports, and SATA2 devices usually work in SATA1 ports. Some SATA3 devices working in SATA1 ports are not unheard of, though.