I think it mostly means that identity-mapped objects which may be expired aren't really compatible. Of course, one could always

    await session.commit()
    user.name  # BlahError: Object not loaded

    # correct
    await session.commit()
    await user.refresh()
    user.name

This might actually make people more actively avoid SELECT n+1, since lazy-loading would error out by default or require an extra await.

Another thing that might not be completely obvious, but sessions and their objects (session×objects = transaction state) are never shared between threads, similarly it would be unwise to share them between different asynchronous tasks.