Post thumbnail is scaled for password protected posts

I just made a classic WordPress theme and the featured images were supposed to be 100% of the container width, like these:

However, for protected posts, WordPress scales the thumbnail image:

It actually works fine whenever I install the theme and view my site but when I go back to the homepage after viewing another post or a page, that happens.

Is there anyway I could stop this from happening? I was assuming the templates and stuff for password protected posts were the same for public posts.