This field:
https://github.com/odoo/odoo/blob/625a648f227325468981a9e4a51e80b44132a45f/addons/stock/models/stock_move_line.py#L40

Allways shows the same value as create_date.

Could it be defined as stock.move related field?

Should it be written here?
https://github.com/odoo/odoo/blob/3c0337673385876922da95296e70a0b7b728f275/addons/stock/models/stock_move.py#L1048

@Tecnativa
""" When the user is encoding a move line for a tracked product, we apply some logic to
        help him. This includes:
            - automatically switch `qty_done` to 1.0
            - warn if he has already encoded `lot_name` in another move line
        """
        res = {}
        if self.product_id.tracking == 'serial':
            if not self.qty_done:
                self.qty_done = 1
            message = None
            if self.lot_name or self.lot_id:
                move_lines_to_check = self._get_similar_move_lines() - self
                if self.lot_name:
                    counter = Counter(move_lines_to_check.mapped('lot_name'))
                    if counter.get(self.lot_name) and counter[self.lot_name] > 1:
                        message = _('You cannot use the same serial number twice. Please correct the serial numbers encoded.')
                elif self.lot_id:
                    counter = Counter(move_lines_to_check.mapped('lot_id.id'))
                    if counter.get(self.lot_id.id) and counter[self.lot_id.id] > 1:
                        message = _('You cannot use the same serial number twice. Please correct the serial numbers encoded.')
            if message:
                res['warning'] = {'title': _('Warning'), 'message': message}
        return res
    @api.onchange('qty_done')
    def _onchange_qty_done(self):