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 


addons/stock/tests/test_move.py
'product_id': self.product1.id,
            'product_uom': self.uom_unit.id,
            'product_uom_qty': 3.0,
        })
        move_stock_stock_1.write({'move_orig_ids': [(4, move_supp_stock_1.id, 0), (4, move_supp_stock_2.id, 0)]})
        move_stock_stock_2 = self.env['stock.move'].create({
            'name': 'test_link_assign_6_1',
            'location_id': self.stock_location.id,
            'location_dest_id': self.stock_location.id,
            'product_id': self.product1.id,
            'product_uom': self.uom_unit.id,
            'product_uom_qty': 3.0,
        })
        move_stock_stock_2.write({'move_orig_ids': [(4, move_supp_stock_1.id, 0), (4, move_supp_stock_2.id, 0)]})
        (move_supp_stock_1 + move_supp_stock_2 + move_stock_stock_1 + move_stock_stock_2)._action_confirm()
        move_supp_stock_1._action_assign()
        self.assertEqual(move_supp_stock_1.state, 'assigned')
        self.assertEqual(move_supp_stock_2.state, 'confirmed')
        self.assertEqual(move_stock_stock_1.state, 'waiting')
        self.assertEqual(move_stock_stock_2.state, 'waiting')
        self.assertEqual(self.env['stock.quant']._get_available_quantity(self.product1, self.stock_location), 0.0)
        
        
        move_supp_stock_1.move_line_ids.qty_done = 3.0
        move_supp_stock_1._action_done()
        self.assertEqual(move_supp_stock_1.state, 'done')
        self.assertEqual(move_supp_stock_2.state, 'confirmed')
        self.assertEqual(move_stock_stock_1.state, 'assigned')
        self.assertEqual(move_stock_stock_2.state, 'waiting')
    def test_link_assign_7(self):