Why is the height of point 2 same as point 3?

[EastWindBreaks]

Homework Statement

Homework Equations

The Attempt at a Solution

Is it an assumption because the difference in height is small?

 

[mfb]

With a setup as shown height differences within the turbine are very small.
For smaller height differences, other types of turbines are used.

 

[EastWindBreaks]

I wonder why it didnt use "≈", thank you!