Yes Closterman has been credited for 33 victories by the French Air Force (FAF counts shared kills as full kills), the RAF credits him for 23 victories. Closterman personal claims are only those attributed to him from the RAF, he repeated it several times in aviations papers all along his life.
The big show is no Sci Fi, no pilot who fly with him ever invalidated what he wrote. Closterman has always been humble and discribed himself as a lucky pilot fighting against aces.
But he was more than a competent pilot, he was clever, as an engineer he had a solid understanding in his aircraft and was experienced as an aerobatic pilot even before the war.
Calling him a liar his plain defamation. The keyboard warrior who produces such an insult should better look himself in the mirror and consider trying to be more like Pierre Closterman than what he himself actually is.