I understand Bildung to be a much richer notion of personal development, including capabilities, intelligences. spirituality (in a non-religious sense) - Bildung results in what used to be termed an Educated Person

Bildungsroman is a novel (like Recherche les Temps Perdu) devoted to the development or formation of a character from childhood. The Bildung part is the development. There is a trace to Pestalozzi in educational thought.

"Literacy," on the other hand, is a very different can of worms in my view. One source traces its use to 1888 (Ohmann, College English 1985). "Illiteracy," was, he discovers, originally pejorative, synonymous with barbarism, etc. It gets rolled into educational discourse in the early 20th century. Yerkes was asked to develop tests for army recruits as a result of WWI, when it was discovered that recruits were too often unable to read. Quantitative measurement was the foundational notion to begin to address this problem.

So there is a lack of direct connection between literacy and childhood development until the middle and late the 20th Century. By then the contributions of Piaget, Skinner, cognitive psychology, eventually Vygotsky began to contribute to a "middle class" notion of literacy in a qualitative sense as well. Cognitivists such as Arthur Applebee were arguing that literate activity, reading and writing, change the way children learn and thereby change the mind and the child's social destiny. At this point, one could begin to link the notion of Bildung with literacy in the literature.

I suppose this lays out the schema by which I understand your question without answering it directly. My direct answer is that while today we automatically (ideologically) assume that bildung or child development necessitates literacy (which in our notion of society is not incorrect), it is nonetheless highly questionable because it is only within our concept of society that development requires literacy, and different degrees of it. Currently UNESCO lists the literacy of nations in the most general and meaningless terms, suggesting that a nation dare not call itself a nation unless it can measure its own literacy. One's notion of self in all important ways is either informed by literacy or significantly of a different order. The difference between development and literacy, in my view, is that while literacy requires a "middle class" or bourgeoisie that aspires to social mobility, meritocracy and oligarchy, development, in and of itself, is the narrative of all children, those who obtain advantage through the concept of literacy and those who are disenfranchised by it. (Don't get me started!)