I think you’ve completely lost the plot again. First it was a sleeping nanny, now you have the abductor actually using subterfuge and engaging in face to face conversation with a nanny, knowing in advance the name of the child they have come to nick or some other convoluted plot and you reckon this is easier than entering an unlocked apartment on a street corner while the parents are out and nicking a kid? Cray-cray.
I respect your opinion and will defend your right to express it.
There's 2 ways of executing - overt or covert. Covert over overt every time. Security I assume would have been nil back then. So you're dealing with one, maybe two staff.
But occasionally subterfuge is required.
It's an operational decision.
Edit: consider the plight of Jimmy the Abductor. Imagine the poor dude hunkered down in the hedge, playing the human version of Frogger with all these infernal passers by and checkers, stopping to chat, nipping up and down the road, some of them carrying other kids (Jimmy wonders if the kid he's got his eyes on has already been nicked!), some going in, some not, some listening at windows, some going for a wazz......he'd be bobbing up and down like VS responding to a contentious post about varieties of meat juice leakage and the efficacy of household cleaning products to remove.