Básicamente de todo el enlace que te pongo donde yo creo que está lo importante para el caso que nos ocupa es en esto (copio y pego):
Guaranteed and Non-Guaranteed Multi-Leg Orders
A Guaranteed multi-leg order is an order where executions are guaranteed to be delivered simultaneously for each leg and proportionately to the leg ratio. Available only for Smart-routed US option spreads and stock/option combination orders. Any risk of resulting execution that does not maintain the integrity of the spread is taken over by IB.
Non-guaranteed spreads are exposed to the leg risk of partial execution, with the remainder of the combination order continuing to work until executed or canceled.
Multi-leg orders are not guaranteed to be executed proportionately to the leg ratio – although every effort is made to execute the order that way.
For a more aggressively routed order, you may check the Non-Guaranteed checkbox at order entry to take on the leg risk inherent in partially-filled combinations orders.
The Non-Guaranteed field can be preset in the order ticket or you may include the additional non-guaranteed field in an order management row.
Make this selection in the Combos Preset page to apply globally to all combination orders using the preset strategy.
On a per order basis, the attribute can be set in an order row field or on the Miscellaneous tab of the order ticket.
Many combination order types that are submitted via the IB trading platform as a combination are not natively supported by the exchanges and therefore may not be guaranteed by IB; this means that a single leg may fill without the entire combination order being filled.
Guaranteed multi-leg orders can be directed to a specific exchange where spreads are natively supported or they may be SMART routed; non-guaranteed multi-leg orders can only be SMART routed.
Non-US Products Smart-routed Combos – You can create non-guaranteed smart-routed combination orders for AUD, CAD, CHF, EUR, GBP HKD, and JPY products. Please note that these non-US combos are always non-guaranteed, which means that a single leg may fill without the entire combination being filled.
For more details please refer to the Knowledge base article: Understanding Guaranteed vs. Non-guaranteed Combination Orders.
Aquí es donde yo creo que un combo a precio limitado de disparo del diferencial para productos NO USA queda descartado.