You are conflating issues, there is nothing stopping a developer from creating a "35-" development (Except a market of course).
And age discrimination in housing is actually illegal, the 55+ and 65+ situations are special exclusions.
I'd be down, that means young people can't actually own houses, unheard of for my generation.
But yes, it's no secret older folk either have better financial safeties that degraded by millenial/Gen Y (pension, social secrutity) and generally make more money. Great market to appeal to. Meanwhile, the 23- market takes out an un-bankruptable 100k over 4 years hoping to climb through the cracks.