Thats not what skinny means.

You've defined skinny as 'medically dangerously low levels of body fat/muscle tissue'.

It is possible to be skinny and healthy.

Ariana Grande is so far beyond skinny that she genuienly needs an immediate medical intervention.

golly that’s not what i understand skinny to mean. i think it’d be odd if “every skinny person is unhealthy” was true by definition

Skinny means you can see the bones.

No, it does not. Your opinion of what a relative term means is not fact.