I always take "might be a medical issue" not as "do nothing," but rather, "don't leap to abuse/neglect conclusions." Could also be another reason why it would be better to approach an authority figure about it rather than the parent directly, because a parent might feel uncomfortable talking to a peer they don't know well about their child's medical condition, especially in a semi-public place on the spot. An authority figure (teacher or principal) could organize a private conference time with explicit guarantee of confidentiality, and they generally have a socially-recognized role as overseers of child welfare.
And yeah, if the symptoms are still so noticeable, any medical intervention hasn't worked yet, but you never know what stage they might be at--maybe they are desensitized and haven't noticed, maybe they are still going to doctors to figure it out, maybe they just started a treatment last week and it hasn't kicked in yet, maybe they have been trying several different treatments and none have worked yet, etc.. So again, not "do nothing" IMO, but even more reason to make sure the proper authorities are aware and monitoring it.