If the videos appear to be playing at a faster speed when viewed in the iPhone Photos app, the issue could be with the Video Format Compatibility. The iPhone Photos app supports a variety of video formats, but it's possible that certain video formats may not be fully compatible. In such cases, the app may attempt to play the video but encounter issues with decoding or rendering, resulting in an accelerated playback speed.
Where did you get those videos from? Please check the source. Videos are typically recorded at specific frame rates, such as 24, 30, or 60 frames per second (fps). If a video is recorded at a frame rate different from what the iPhone Photos app expects, it can cause the video to play back at an incorrect speed. For example, if a video was recorded at 24 fps but the app expects 30 fps, it may play back faster to compensate for the frame rate difference.