Hi, the code from the other support query is for removing the post’s featured image which is displayed as background image behind the post title, like this post in our demo.
In the ‘Latest’ theme the featured image is only displayed as the title background if the image width is greater than it’s height (landscape ratio).
In your linked post however, the featured image is higher than it is wide (portrait ratio), so to remove the featured image in this case, add the following to Customize > Additional CSS:
.single-post .featured-image {
display: none;
}