Section 250.64(A) states that aluminum and copper-clad aluminum grounding electrode conductor terminations located inside listed equipment suitable for the location are considered separated from the earth, even if the enclosure is an open bottom switchboard.

There are many open bottom switchboards that are listed for wet locations and provide protection for the terminations inside.

The NEC^® considers the inside of a raceway installed outdoors as a wet location but does not consider the interior of an enclosure as a wet location unless the enclosure is installed underground.

If installed external to an enclosure and outside a building, aluminum or copper-clad aluminum grounding electrode conductors are not permitted to be terminated within 18 inches of the earth.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC^® edition of NFPA 70.

2020 Code Language:

250.64(A) Aluminum or Copper-Clad Aluminum Conductors. Grounding electrode conductors of bare, covered, or insulated aluminum or copper-clad aluminum shall comply with the following:

(1) Bare or covered conductors without an extruded polymeric covering shall not be installed where subject to corrosive conditions or be installed in direct contact with concrete.

(2) Terminations made within outdoor enclosures that are listed and identified for the environment shall be permitted within 450 mm (18 in.) of the bottom of the enclosure.

(3) Aluminum or copper-clad aluminum conductors external to buildings or equipment enclosures shall not be terminated within 450 mm (18 in.) of the earth.