4K 60FPS Video Capture Frame Rate Drop

When recording 4K 60fps on iPhone 11 Pro, 12 and 13 it does not provide a stable frame rate of 60fps. Checking the Meta data it ranges from 52-58. Are there any settings that can force 60 frames or anything I can do to get a stable frame rate of 60fps. it also appears when trimming the video the frame rate drops as well.

4K 60FPS Video Capture Frame Rate Drop
 
 
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