According to the GM/Cadillac representative in this Racer.com article, they are still committed to IndyCar as well as competing full time in the WEC with our all-new Cadillac V-LMDh. So yes it would appear Andretti is using the power and branding of a big manufacturer to get into F1.
https://racer.com/2023/01/05/propose...dycar-program/