Is it possible to learn a complex skill like reading by osmosis?

The shirt answer: yes. The somewhat longer answer:

Learning reading by osmosis is not going to happen by accident. It will only happen if a child is systematically read to, preferably daily, and allowed to view the pages as they are being read. It will also be helpful to draw their attention to the text, even in a general manner.

The capacity for such ease in learning may depend on the measure in which the learner is intellectually gifted, because giftedness will enable them to easily notice patterns in the text and, in due time, associate them with the corresponding sounds of speech as the text is being read aloud.