Impacted versions:
11.0

I don't know if it is an issue, but I think is strange.

`product_qty` is in unit of `product` : https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L240
`reserved_availability` is in unit of `stock.move` : https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L295

`move.product_qty - move.reserved_availability` seems to have no sens, no ?

https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L915
https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L917
https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L924

thank for your answer

@jco-odoo 
@alnslang 


move2._action_done()
        self.assertEqual(move1.state, 'confirmed')
        self.assertEqual(move1.move_line_ids.qty_done, 15)
        self.assertEqual(move2.state, 'done')
        stock_quants = self.env['stock.quant']._gather(self.product1, self.stock_location)
        self.assertEqual(len(stock_quants), 0)
        customer_quants = self.env['stock.quant']._gather(self.product1, self.customer_location)
        self.assertEqual(customer_quants.quantity, 30)
        self.assertEqual(customer_quants.reserved_quantity, 0)
    def test_availability_5(self):
        """ Check that rerun action assign only create new stock move
        lines instead of adding quantity in existing one.
        """
        self.env['stock.quant']._update_available_quantity(self.product2, self.stock_location, 2.0)
        
        move = self.env['stock.move'].create({
            'name': 'test_edit_moveline_1',
            'location_id': self.stock_location.id,
            'location_dest_id': self.customer_location.id,
            'product_id': self.product2.id,
            'product_uom': self.uom_unit.id,
            'product_uom_qty': 4.0,
        })
        move._action_confirm()
        move._action_assign()
        self.env['stock.quant']._update_available_quantity(self.product2, self.stock_location, 4.0)
        move._action_assign()
        self.assertEqual(len(move.move_line_ids), 4.0)
    def test_availability_6(self):