My impression is that there are a lot of 'Chinese whispers' where Chiron's war record - or lack thereof - is concerned. He seems almost to go to ground in 1940; in November of that year Maurice Henry, in l'Auto, names him as one of several possible candidates for what they hoped would be a 'Director of Mechanical Sports' under Vichy (the 'bounding Basque' Jean Borotra was of course the Vichy Sports Minister) - but as the list also includes Wimille, Sommer, ‘Raph’, Étançelin and Benoist it was probably just a bit of kite-flying. He was re-elected to his post at the AC de Monaco the next month, but, after that, I've found almost nothing until 1946 when the Journal Officiel de Monaco records that 'La Médaille de Première Classe de l'Education Physique et des Sports est attribuée à ... Louis Chiron, ancien Champion du Monde (Automobile)'. [Which is news to me!]
https://journaldemon...d9a6e0c3ed1.pdf (page 3, col 1)
The wartime archives of the principality are still closed, so that's pretty much a dead end, and there is AFAIK no reliable history of the war years there. Monaco was of course officially neutral throughout the war, although it was occupied by Italian forces in November 1942 and then by the Germans after the fall of Mussolini. So presumably travel to Switzerland would have been impossible once the Italians arrived, and then until the German withdrawal in early September 1944; Monaco was liberated by US paratroops on September 8th.
I do wonder if the suggestion about downed airmen may be a confusion with the work of Pete de Paolo, who - as a USAAF officer - was responsible for the well-being of US aircrews who had force-landed in Switzerland and had been interned.
Chiron is mentioned here, in a Swiss paper from June 1942, as being a participant in a meeting of 'anciens pilotes' in Paris:
http://doc.rero.ch/r.../1942-06-17.pdf (page 7)
The same newspaper says in March 1943 that Chiron is 'on the Riviera, whence he originates'.
Those are the only two mentions I've found which mention his whereabouts - and both put him in France and/or Monaco. Nothing in the Swiss press suggests he was in Switzerland.