some possible reasons to investigate: 1. older videos have a larger file size because they are encoded less efficiently (h264 vs h265) 2. gigabytes vs gibibyt

some possible reasons to investigate: 1. older videos have a larger file size because they are encoded less efficiently (h264 vs h265) 2. gigabytes vs gibibytes (like how a 500GB drive formats to ~465 GiB) 3. rounding errors 4. Apple fucking its customers 5. combo of the above