From what I can tell, this doesn't really look like granny chic, to me, it looks late '70s/early '80s inspired; so, assuming the average age on this forum is around 25, it's more what mummy wore when she was young, than what granny wore (of course, mummy might now be a young granny to very young children, herself, but that doesn't mean she's granny to most of the posters here, yet [I presume?!]).
I'd have thought that granny chic for a 25 year old would, presumably, be what granny wore when she was young; so 1950s stuff, predominantly.
Admittedly, some people's grannies might have started wearing this stuff in the early '80s, when they were around 50 and still be wearing it now.
But, that will pretty much always be the case, as it's unavoidable that some older people will continue to wear fashions until they come around again, 25 years later!
Of course, if what is meant by 'granny chic' is that it is all very buttoned-up and conservative looking, with very little skin showing, with the amount of flack that is generated by the sight of anything remotely sexy, on this forum, I suppose it is inevitable that most designers will prefer to play it safe and produce rather asexual/androgynous collections?