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
self.assertEqual(len(picking.move_lines), 2)
        scrapped_move = picking.move_lines.filtered(lambda m: m.state == 'done')
        self.assertTrue(scrapped_move, 'No scrapped move created.')
        self.assertEqual(scrapped_move.scrap_ids.ids, [scrap.id], 'Wrong scrap linked to the move.')
        self.assertEqual(scrap.scrap_qty, 5, 'Scrap quantity has been modified and is not correct anymore.')
        scrapped_move.quantity_done = 8
        self.assertEqual(scrap.scrap_qty, 8, 'Scrap quantity is not updated.')
    def test_scrap_5(self):
        """ Scrap the product of a reserved move line where the product is reserved in another
        unit of measure. Check that the move line is correctly updated after the scrap.
        """
        
        self.env['stock.quant']._update_available_quantity(self.product1, self.stock_location, 4)
        
        partner = self.env['res.partner'].create({'name': 'Kimberley'})
        picking = self.env['stock.picking'].create({
            'name': 'A single picking with one move to scrap',
            'location_id': self.stock_location.id,
            'location_dest_id': self.customer_location.id,
            'partner_id': partner.id,
            'picking_type_id': self.env.ref('stock.picking_type_out').id,
        })
        move1 = self.env['stock.move'].create({
            'name': 'A move to confirm and scrap its product',
            'location_id': self.stock_location.id,
            'location_dest_id': self.customer_location.id,
            'product_id': self.product1.id,
            'product_uom': self.uom_dozen.id,
            'product_uom_qty': 1.0,
            'picking_id': picking.id,