I’m callin’ BS on this one. Even ignoring the S-band radar vs. anti-air radar threat receivers issue, the Sidewinder is an air-to-air intercept missile (and uses an infra-red targeting system). The HARM anti-radar missile would be the appropriate ATG ordnance for the situation...
Since the graphic uses quotes around the response by the RAF, I’m assuming they are repeating it verbatim... in which case either the RAF officer is completely incompetent, or the “quote” is made up completely...