Why does an edited 4K 60 FPS video become significantly smaller than the original when exported from the Photos library?

I'm observing an interesting behavior on iOS when uploading edited videos from the Photos library.

Scenario

Device: iPhone

Video: 4K, 60 FPS

Original video size (Photos app): 660 MB

Uploaded original asset: 660 MB

After applying a simple edit (e.g., a filter) in the Photos app:

Photos app still shows the edited video. When my app uploads the current/edited asset, the uploaded file size becomes 167 MB.

So the edited version is approximately 75% smaller than the original (660 MB → 167 MB), even though the duration appears unchanged.

Questions

1. Is this expected behavior for edited videos in the Photos library?
2. Does iOS automatically re-encode edited videos using a lower bitrate or a different codec (e.g., HEVC) when generating the current rendition?
3. Does the Photos app continue to display the size of the original asset rather than the size of the edited rendition?

I'm aware that PhotoKit allows retrieving both the original and the current (edited) versions of a PHAsset. In this case, I'm intentionally retrieving the current version, and this behavior is observed only for the edited asset.