His chapter on the 3 May 1945 is certainly not the most historical of the book. He writes that a huge air battle opposed numerous German fighters to 122 Wing, that claimed 14 fighters shot down (and numerous floatplanes and transports) against TEN losses. AFAIK there was never a day when ten Tempests were lost in air combat, and certainly not this one.
According to the victory list available at
http://cieldegloire.com/004_clostermann.php, Clostermann claimed four aircraft destroyed on 3 May 1945 (2 Do 24s, a Ju 52 and a fw 190) but the unit ORB listed them as "destroyed on the ground". That is more likely than the furious battle described in "Le grand cirque".