Upon uploading videos through an HTML 'input file' element, they are identified as image/jpeg with .jpeg extensions though the file size remains the same. What is happening and why?

I am trying to upload some of my videos to a website, though for troubleshooting I even tried the w3 schools input button to understand what was happening.

https://www.w3schools.com/tags/tryit.asp?filename=tryhtml5_input_type_file

All the videos I am selecting (I know these are not images, they are 2-3 minutes long and sharing them by email for example maintains their original movie extensions) are identified as image/jpeg types with the extension .jpeg while staying their original file size.

Why does my iPhone convert these videos in such a way that the web identifies them as pictures?

I wanted to know if this problem was unique to my device so I tried an iPad and three other iPhones. One other iPhone experiences this problem like mine but the others are fine.

What is going on?