No reassessment needed
"reassess the role of countries that remained ostensibly neutral in the conflict, such as Spain and Sweden, since it appears governments in both those countries were in regular contact with the Axis powers."
Duh, of course they were. If you were in charge of a neutral country in WWII, especially one bordering Axis occupied territory, wouldn't you talk to them?
Have they forgotten Raoul Wallenberg, who was able to save thousands of Hungarian Jews because he was in Axis Hungary as a *diplomat*? See also Folke Bernadotte - grandson of a Swedish king - and his role as Vice Chair of the Swedish Red Cross in diplomatic efforts on behalf of POWs and people in camps.
Sweden sold Germany iron ore: no iron ore, no need for the Germans to invade Norway to ensure continuity of supply via Narvik, no fall of Chamberlain because of the mess up of Britain's reaction caused in part by Churchill's plan to invade first, possibly no Churchill as PM.
Spain had Franco in charge. Germany wanted access through Spain to attack Gibraltar. The British bribed Franco and various other people to say no, despite the fact that Franco owed the Axis big time for the help they'd given in the Spanish Civil War.
Both countries were used extensively by both sides for government to government contacts, both openly and in attempts to plant false information. When various Nazis realised the war was lost, they talked to a representative of Roosevelt... in Stockholm. Does anyone think the Swedish government didn't know?
See also Switzerland, Turkey, etc etc etc.