You need the 'flashcards' before you can read, listen or talk. Go try reading a book where you don't know most of the words. Heck you need 'flashcards' before you needs 'flashcards for words'. You need to memorize the alphabet first. Try reading a text where you haven't learned the writing system.
> Young children do not use vocab flashcards to learn their L1.
Because they can't read.
> They aren’t being “drilled” to learn “mama.”
Obviously you aren't a parent. You think a child magically decides one day to say mama? Or do you think it's the mother constantly saying 'mama' to the child until the child 'remembers it' and repeats it?
> They have actual needs in an actual social context and attend to nuanced details of that context to make complex statistical inferences about the world, their perceptions, and their body.
What? Complex statistical inferences about the world?