A rod at the array is a good thing, in my opinion.
This keeps the array at the same zero potential as the earth around it.
Based on some recent investigation I've been doing regarding grounding of solar arrays (and say, satellite or outdoor wifi / telecom equipment towers).
The is some strong evidence I've been seeing, indicating that fully grounding towers and solar array ground mounts to a copper ground rod could help to attract lightning strikes into these locations.
Just to sum it all up in short form. I am finding that lightning/surge arrestors inline with the PV circuit conductors' run (and grounded to a copper ground rod at the array or tower location) is a great thing.
But grounding the array mount / solar panel chassis to Earth, may not be as desirable. My thought is to perhaps leave the array ungrounded and try to insulate it from ground (or just leave it at whatever Earth-ground delta it already is at), and use a resistor between the actual ground rod and insulated or semi-insulated array (to help keep voltage potential at zero or close to it, like from wind and static electricity buildup), but not actually providing a solid 0 Ω ground.
Obviously, there are a lot of metal-based ground mounts which would be naturally grounded to various degrees anyways, so this may not be easy to control (to insulate the ground mount or tower).
It could simply be more effective to place lightning rods at other locations on the property in question, to help draw lightning strikes away from the tower or array location (and just allow to fully ground those fixture arrays).
I do know that when we used to build WISP towers (at an old job I had), we would generally ground towers, but not chassis ground the radios themselves to the tower chassis (as they had plastic housings anyways). But we'd use shielded CAT5/6 cables which would carry the equipment circuit board grounding, to connect through the ethernet cable shield, which would go down to the Ethernet surge protection devices on the ground, which have their own Earth grounding connection to the ground rod, but towers themselves would ground on a separate path.
I don't have all the answers yet in planning for my own ground mount install I will be doing soon. I definitely know it is true what you say that we want to keep that zero potential, but also, can we design the system in a way as in not to help encourage lightning strikes towards our equipment? Would it be better to use a resistor in these cases to allow most voltage deltas (between equipment chassis ground and Earth ground) to balance out, without creating a 0 Ω connection from array chassis to Earth ground?
Or in my case, my array mount will be around eye level height (right next to my steel building), which my steel building will be a much taller structure. I wonder if putting lightning rods on the peak of the building ridge (away from the array), or to build actual lightning rods towers on the ends of the property would be more effective at keeping lightning away from the arrays and structure. We do get violent lightning here and it is a fairly empty valley (no trees or other buildings by me), where I worry a bit about being one of few lots in an open field (with metal conductor all over it).
Or is it even in my power at all to try and control somewhat what the lightning will do hehe...