We had an 87 post thread about whether or not a supply side tap is a service disconnect a few threads back, which I'm not going to link to. :roll: You can find it, and a few others on the subject, if you search past threads.
The point is...
If the disconnecting means for the supply side tap is considered a service disconnect, then article 250 requires a GEC to be run from the electrode(s) to the disconnect.
If not, then there is no such requirement. You could run an EGC back to the location of the normal service disconnecting means.
My advice is to do it whichever way you prefer, as long as everything is safely bonded, but make provisions for doing it the other way in case your AHJ disagrees with you.
None of what I've just said should be construed as requiring a GEC from the inverter for DC system grounding. On a transformerless inverter, I agree that under the 2014 code only an EGC is required. The GEC I'm talking about would only go from the supply side disconnect to the electrode.