It is true. You need only trouble yourself to search. Here's a recent paper, for example: https://jamanetwork.com/journals/jamainternalmedicine/articl...

> if what is detected is small enough for that there's no reason "treatment" can't just be monitoring it's size with follow-up scans.

This is false—it is exactly what the article is trying to convey. There is a risk to any test, and one of the major risks for imaging is getting treatment for things that would never cause symptoms or require intervention.