I encountered the phrase "Except, maybe not" when reading an on-line article. I guess it would probably mean "It (what mentioned earlier) may not be right, and there are some exceptions". Is my understanding correct? Is the phrase common?

Below is the original sentence.

"The consensus has been that when you get older, your arteries will clog with plaque, and your odds of having a heart attack or stroke increase. Except, maybe not."

https://www.healthline.com/health-news/how-to-have-younger-arteries#1