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 


""" In a picking with a single partially available move, clicking on validate without
        filling any quantities should open a wizard asking to process all the reservation (so, only
        a part of the initial demand). Validating this wizard should open another one asking for
        the creation of a backorder. If the backorder is created, it should contain the quantities
        not processed.
        """
        partner = self.env['res.partner'].create({'name': 'Jean'})
        self.env['stock.quant']._update_available_quantity(self.product1, self.stock_location, 5.0)
        picking = self.env['stock.picking'].create({
            '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,
        })