I don't think that's right.
Our ICOM setup, setup according to the installation instructions, has a heavy green yellow/wire from the SSB ground connection to the AT130 tuner.
Then there is a heavy green/yellow wire from the AT130 tuner to the bolt connection in the lazarette which has copper tape connecting that bolt to the sintered bronze plates on the skeg.
If you don't connect it like this , where does the ground for the SSB transmitter go? ... certainly NOT to the bonding system.
In our ICOM SSB, the transmitter ground is internally connected to the 12V negative supply line, hence the need for an isolated power supply so that there is no connection between ground and 24V negative, which would compromise the bonding system via the seawater path between the sintered bronze plate and the anodes.