> average Nordic Baltic person

there is no average person, it is a myth of statistics.

A meaningless distinction and unnecessarily nitpicky. From a scientific perspective it's not a myth, it's a valuable tool. For the average person (see what I did there?) it's not a mathematical formula, it's way of saying "that person whose characteristic being discussed is very common and representative of the whole group".

All models are wrong, but some are useful.

An average person has one testicle and one ovary.

That is a mean person