Historically if you wait multiple days / weeks to give them a chance to reply they just do an end-run and publish puff pieces in major outlets to try and defuse your article. There are multiple cases of this in the past year.
It's either investigative journalism or it's not. How long you wait for comment has nothing to do with that. Do you really think this is equivalent to tabloids posting faked photos of some movie star's belly?
How long did they wait before publishing? We don't know, it doesn't matter. Simply stating that they didn't respond had the desired effect, and - as you rightly pointed out - does nothing to diffuse the story. The implication of the story being that not only are Google potentially taking advantage of vulnerable people to further their unspoken, morally grey agenda, but it may also have a racially questionable angle.
Alternately, they wanted to train their facial recognition dataset with certain characteristics on the cheap.
That in itself is interesting, but probably wouldn't get as many clicks. It's bottom drawer "I leave you, dear reader, to draw your own conclusions" stuff.
It's either investigative journalism or it's not. How long you wait for comment has nothing to do with that. Do you really think this is equivalent to tabloids posting faked photos of some movie star's belly?