It depends on what system is being used and what airline you are dealing with. For instance, any Apollo/Galileo agency or booking engine will be seeing live UA availability just as any UA res agent would. The confirmation is automatic. Some systems have a direct link availability, but I would almost guarantee that the web-based engines don't use this. Some airlines will "guarantee" the seat if booked through the direct link and it shows availability , even if there isn't. Otherwise, it can take from seconds to hours for an airline to "bounce" the reservation booked from a 3rd party source.

Also "claiming" the seats is different than storing the fare. You may reserve a "Q" seat and it may be yours, but if new fares are loaded before the fare is stored... you know the conclusion.