Noskova, a 21-year-old Czech, needed only 86 minutes to capture the Group One match over Ukraine's Kostyuk with Americans Coco Gauff and Jessica Pegula to play later.
World number one and reigning champion Elena Rybakina withdrew from the WTA Finals on Saturday due to a viral illness with Kostyuk replacing her at the California hard-court event.
Noskova improved to 3-1 against Kostyuk, all matches coming this year as both made the WTA Finals for the first time.
Noskova won in three sets at the US Open fourth round in their most recent prior meeting and in the Wimbledon semi-finals, while Kostyuk won on her way to the Madrid clay crown.
Gauff, the 2023 US Open and 2025 French Open champion, and Pegula have split 10 career meetings, Gauff winning the Cincinnati final and a Wimbledon quarter-final this year in their most recent matchups.
This year's WTA Finals were scheduled to be held in Saudi Arabia but in July were moved to Indian Wells after US military strikes on Iran in February and the subsequent war in the region.