ProRes video recording is limited to 1080p at 30fps on iPhone 14 Pro 128GB models. 4K ProRes video recording requires 256GB, 512GB, or 1TB models.
The lack of support for 4K ProRes video recording on the 128 GB models is probably due to the heavy weight of such videos. Apple said that one minute of 10-bit ProRes video is about 1.7GB at 1080p and about 6GB at 4K.
Source: Ferra
