Further these are the bylaws covering the area:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/39585/imber_range.pdf

They are the Imber Byelaws 1963. There is a big sign in Imber with those bylaws on it. To wit byelaw no. 3 starts, "The Danger Area shall be permanently closed to the public. Subject to the provisions of Byelaw No. 8, no person shall:-

"(a) enter into or upon or pass over or through the Danger Area, or
"(b) be or remain in the Danger Area, or
"(c) cause or permit to suffer any vehicle, animal, aircraft or thing to enter into or upon or to pass through or to be or remain in or upon the Danger Area, or
"(d) cause or permit any aircraft to fly over the Danger Area at a height less than 30,000 feet above mean sea level."

That is absolutely NOT permissive access to the area as defined by OSM tagging schemes. Permissive access means generally open to the public with a permission which may be revoked. This is the opposite. It is generally closed to the public with permission for access to the village occasionally granted.