I should have included the link in the quote concerning cca/ca and copper being the culprit as I do not know if this is the reason, or the sole reason for the increased reactivity vs older treated lumber. A quick search says " ... chemicals used to treat this wood were revised in 2003 to remove some of the potentially harmful elements in the treatment. The change in chemical formulations increased the corrosivity of the wood when in contact with metal parts. The two most popular chemicals for wood pressure treatment are alkaline copper quaternary (ACQ) and copper azole (CA), which are both active corrosion materials. ... " American Galvinizers Association I do use special fasteners when building decks with treated lumber.It’s the acidic action of the treatment agents that is the major problem with pressure treated wood, not the copper.
CCA plywood in aluminum boats, for example, never caused short-term issues, nor did it create failures of fasteners with high rise building balconies or the semi truck aluminum trailers that delivered from the plants to the yards of retailers and distributors.
Aluminum and stainless DOES make for bad juju, but for whatever reason it seems to go years without issue in boats, especially when painted. I don’t know why because on paper: it shouldn’t.
Thinking out loud ...
I have only used marine grade plywood in boats. The main difference between marine grade and 'reg' grade is in the glue. AFAIK, it is not treated, although, if using treated wood, it would stand to reason that a nonporous painted surface between the differing materials, might, mitigate a reaction. Curious, do you know which wood treatment method was used in the applications you mention?
... and with a bit more research, it appears not all treated lumber is cca/ca and may actually be aluminum friendly.
Back to the OP and mounting panel sheathing directly to what is basically a pole barn. The OP may be able to source the aluminum friendly lumber, or possibly a simple barrier of paint between the panel's frame and lumber might suffice. It would be interesting to know the long term outcome.