It is a puzzle. Why would the French invent encountering Bf109s? It makes no sense, even if we discount the claims (and it seems that the French did award at least "probable" victories). The reports by Montravel and L'Espinay are very descriptive about the damage they inflicted on the Bf109s, one of which lost part of it's tail, the other was trailing black smoke. The French pilots only saw six Bf109 but perhaps there were others? Montravel claims he attacked four.
Could it be a "blue on blue" incident? A Spitfire or a Mustang flight? I am sure you've considered this too. The dogfight was lengthy and the French pilots had to drop their wing tanks when entering the combat.
I should mention that I have been researching the French fighter squadrons claims from 1939 and it's rare to see evidence of overclaiming where no LW were at least damaged. Montravel was a veteran flyer and deputy commander of GC2/5 and had claimed victories in the Battle of France, L'Espinay had several months of combat against the Luftwaffe in Tunisia in 1943 and led the "Sioux" Escadrille (SPA124).
Something is missing. I am sure the French flight attacked what they saw as a formation of enemy fighters and someone got hurt. I just have to live long enough to see it proved
best regards
Keith
p.s. I read your very detailed account of the Saint-Exupery case. Great stuff!