Thanks, great question!

For autoencoders, the encoder and decoder are two separate networks and usually not invertible. A Normalizing Flow is bijective and applied in one direction for encoding and the other for decoding. That means that you obtain the exact same image after encoding an image into latent space and decoding it again.

You might be interested in the following paper:

SurVAE Flows: Surjections to Bridge the Gap between VAEs and Flows

Does that answer your question?