RAF rules in my time were that the flying badge could only be retained upon reaching CR status on a squadron. Until then, in effect, it's worn only a probationary basis.
One of my colleagues through training failed to reach CR and he eventually re-mustered to the education branch. He was no longer allowed to wear his wings. Very disappointing for him but that was the rule. As far as I know, this rule hasn't changed.
If Siam didn't reach CR, then he's not entitled to wear RAF wings, Endex. To do so is dishonest.