Handkerchief material

yay first post here

So upon reading Fluesser and lurking it seems that to be stylish one must not wear a pocket square as the same material as the tie. Why is it that most pocket squares we buy from the fashion stores are made of silk, which most ties are made out of?

And just to verify, is it then the epitome of style to use an actual cotten handkerchief (for sneezing), and those larger silk/polyester hankdercheifs as a pocket square since it is not the same material as ties(silk)?

Also, almost all people I see wear the same combination pocket square and tie and I almost feel it is going against the norm, (maybe even taboo?), to differ from this style.