Yup this is not a crack. I've been working with steel for years and this shows no signs of stress around the area of the opening. Top part is cut too smooth, there should be shearing and large burrs on the edge.
The lack of discoloration or equipment markings in the paint is very interesting, especially the smooth(intentionally cut) part of the opening. I'm not sure how I would do that If I had to reproduce it.
The ultrasound signal is very interesting. The high frequency is one thing but you would need a good amount of amperage to cut into a steel beam like that. Which again also brings up the lack of paint discoloration or equipment markings.