Originally Posted by
jaro
Is there an engineering explanation for this, ie why turning them off will help as opposed to keeping them in airplane mode? I'd be curious what the manufacturer's manual (ie A320) says too but I can try to Google for a pdf

It’s all to do with multi-path interference. Given the modern RF shielding it’s really an over hang for days of older tech, but still belts and braces for unforeseen new tech that may cause interference.