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 


move_line.qty_done = 1
        move._action_done()
        self.assertEqual(move.product_uom_qty, 1)
        self.assertEqual(move.product_uom.id, self.uom_dozen.id)
        self.assertEqual(move.state, 'done')
        self.assertEqual(self.env['stock.quant']._get_available_quantity(self.product2, self.customer_location), 12.0)
        self.assertEqual(len(self.env['stock.quant']._gather(self.product2, self.customer_location)), 12)
    def test_availability_8(self):
        """ Test the assignment mechanism when the product quantity is decreased on a partially
            reserved stock move.
        """
        
        self.env['stock.quant']._update_available_quantity(self.product1, self.stock_location, 3.0)
        self.assertAlmostEqual(self.product1.qty_available, 3.0)
        move_partial = self.env['stock.move'].create({
            'name': 'test_partial',
            'location_id': self.stock_location.id,
            'location_dest_id': self.customer_location.id,
            'product_id': self.product1.id,
            'product_uom': self.uom_unit.id,
            'product_uom_qty': 5.0,
        })
        move_partial._action_confirm()
        move_partial._action_assign()
        self.assertAlmostEqual(self.product1.virtual_available, -2.0)
        self.assertEqual(move_partial.state, 'partially_available')
        move_partial.product_uom_qty = 3.0
        move_partial._action_assign()
        self.assertEqual(move_partial.state, 'assigned')
    def test_unreserve_1(self):