If I create a new field in an order and then a related field in the picking form like this:

 class sale_order(osv.osv):
    """Add comments"""
    _inherit = 'sale.order'

    _columns = {
        'comments': fields.text('Notas internas'),
    }

class stock_picking(osv.osv):
    _inherit = "stock.picking"
    _columns = {
        'comments': fields.text(related='sale_id.comments', store=True),
    }

But if I modify it afterwards it gets updated. Any idea why it does not get updated / set on creation?

Thank you!