IB's terminology is unusual, possibly because its working language is Spanish, but you ought to be fine. I bought a one-way cash ticket out of ORD in J a month ago, and I was also surprised and slightly worried when I saw the "Holding Confirmed" note you're referring to in my booking. Both flights in the itinerary are in January, they are still operating, and IB is still selling seats on both. I have a ticket number, a receipt for the payment, and I've been able to select my seats on both flights.