That's a very good deduction, I'm no physics major, but it visualizes well enough. There always seems a vibration feels more pronounced at one spot, usually not midpoint. Certainly mechanical conditions alter what vibrations would do on their own.
And why some boring bars have a taper that work well, while others might have taper yet can't generate a decent cut. It's worse in unprogrammed milling machines; having limited feed rates compared to any lathe.