This thread alludes to the fact the current is shown on the GX device.
The question is if it’s subtracted from the battery monitor in the multi plus.
And I wouldn’t look at it as a bummer, it gives you a reason to get a smart shunt. In my very early days of Victron “addiction” I was along the same lines thinking why do I need a BMV if the multi plus monitors the SOC, the smart shunt didn’t exist yet, after having a battery monitor and seeing the difference in accuracy I wouldn’t install a system without one.
Especially in your case without a monitored load, the Phoenix.
Trying to ascertain SOC from voltage levels of Li batteries is never going to be accurate as the change in voltage could be 0.01v for 20%
If you do don’t forget it needs a ve.direct to usb as well.
It all depends how much you value having backup power without burning fuel. Which is essentially burning $$$.
In my country a smart shunt costs about the same as 4 x 20l Jerry cans of fuel.