Pattern file generated from template file after overwriting theme

Hello,

I noticed that after adding an image to one of my template files, then overwriting my theme, a new php pattern file was automatically generated and the html was stripped out of the original html template file and added to the new php pattern file. Is this supposed to happen? Here’s a Loom showing what happens: https://www.loom.com/share/3c5f366e271249daa9da704bab5e1b8a?sid=b2cba1b6-593a-4c17-8ac8-c0ae57688ad3

Thanks!