Replacing images with new filename

Hello and thanks for this great plugin!

When choosing the second option “Replace the file, use new file name and update all links” it is stated that “Please note that if you upload a new image, only embeds/links of the original size image will be replaced in your posts.”

What does that mean exactly?

I tested with a page where I inserted all 4 existing thumb sizes of an image and then replaced using this option and all 4 thumbs were replaced correctly. Do I miss something here?

Thanks.