I modify images all the time, for the purpose of correcting lighting problems when they were photographed. I deliberately under-expose digital images for that purpose, because reflected glare that goes to white is not correctable. My goal in doing that editorial work is to portray the image as I saw it as accurately as possible. How is such a problem?
Hence, for the article to say "modified" as if it were bad without discussing what those specific modifications were is beyond confusing.
I was a professional photographer. Manipulating images was something i did most mornings. However, whenever i shot as a photojournalist, manipulating the image (other than cropping) was not allowed. They wanted a “raw” image.
I would think in “science” you would want all of the images to use the same “baseline.” If you want to show A and then B, you really cannot make any adjustments to color or contrast.
I did not read deep enough into the article to find out what they actually did. An educated guess is that they adjusted some of the basic items (brightness, contrast, etc) to make the images “stand out.”
What might not matter to us, would be forbidden in a journal.