As for 'social constructs', tricky topic, and I'll have to watch the video at some point, but chiming in randomly I would say....
'Normality' IS quantifiable, to the point you could define it literally as being the IQR*1.5 of a given set of observations (generic outlier detection). But 'normality' changes over time, and people's perceptions of 'normality' vary hugely. These perceptions are also often not based on adequate observation, or observations at all such as inherited perceptions (which would be where the social construct element sits imo).
For example, one may expect an American to think it is 'normal' to have a BMI of ~25-30. In America this is largely true, but in Japan, that may be considered abnormal, where 'normal' would be more like ~20-25.
Statistics would bear out the quantifiable nature of the above assertion of what is 'normal' in both regions, but the 'social construct' is the subjective belief of the individual American or Japanese person that they are 'right'.
There are all sorts of reading material on Groupthink, confirmation bias and so on that could derail this thought, but I think my main issue lies where perceptions of 'normality' are used as a tool for prejudice without appreciation that perception is almost always skewed by one's environment and upbringing. It becomes dogmatic, and people use statistics that best reflect themselves to make their argument (inherently fallacious.... and why I didn't choose Australia or England in my analogy).
I believe (perhaps fallaciously) that social constructs are a 'normal' phenomenon, where humans by and large are pattern recognition machines and do so consciously and subconsciously. It is absurd to me to expect people not to group and classify based on observation, but it would also be absurd for one to think they have nearly enough training data from their observations alone to make a firm conclusion about those groupings.
A social construct may largely be a shared perception, and in many scenarios may be beneficial to simplify things, but that alone does not constitute evidence of it being 'right', only the basis of a hypothesis that it could be.
In closing, I do not respect anyone who feels the need to assert and dictate their perception of 'normal' is 'right' and allude that being 'abnormal' is 'wrong' without peer-reviewed evidence. And even then that evidence is rarely ever absolute and may be superseded in the future.
Your BMI of 27 may be entirely 'normal' where you live today, and your friends and neighbors may agree, but that does not make it 'right', or even healthy
Instead, I would always suggest to err on the side of "Be excellent to each other. All we are is dust in the wind".
