manual says under normal driving conditions, you shouldn't have to change it.
Under severe driving conditions change every 60,000 miles.
The exact words in the manual are "no check, No service required" for automatic transmission fluid.
Only worry about it under severe conditions
BMW went to "lifetime" fill on auto transmissions fluid back in the 2000s. Justification was better built transmissions and higher tech synthetic fluid allowed for no changes. After a number of year's BMW eventually defined that "lifetime" equaled 125K miles.
My guess is similar is in place here. My BMW mechanic advised back then, (for BMWs) that if you don't change at 60K then don't risk it and drive it until it breaks. He saw many tranny failures occur right after high mileage transmission fluid changes.
Again; that was BMW and not Kia, but similar may apply here. My take is change fluid at about 60 (if conditions apply) or drive it until you define its "lifetime." I'd also worry about finding qualified technicians as this seems like something few if any will have much experience with, so pick wisely if you decide to "break the seal".
I have experienced that a flush later in the trans life can have a negative effect versus drain and refill.
I have a couple friend get performed a flush and with 1-2 years the trans gave up.
The flush later in trans life might stir up particle and material and allow them to pass along the internal NARROW passages of the transmission and cause issue. I was told from several mechanics that about 100K you should just drain and refill.
I would feel better that at some point new fluid synthetic or not would better the transmission verses "never" changing.