For a very long time in feminism, femininity has referred to gender stereotypes and female has referred to sex. This was also the WHO definition.
So yes, long hair is one of the primary markers of femininity across very many cultures, including our own. There’s a whole chapter devoted to long hair in Brownmiller’s classic book on gender stereotypes... femininity.
It is not the same thing as femaleness.
It seems very odd to complain about trans activists misusing the words which refer to biological sex but then also complain about people using the word femininity accurately to refer to things other than sex.
There is no issue with Paris Lees advertising Pantene.