Consider the experimental setup for Young's Double Slit Experiment:

Here there is an angle between the directions of propagation of waves ,i.e., $\angle S_1PS_2$

My question is:

Why is this angle never taken into account while analysing this experiment or the diffraction experiments?

Source of the image: https://www.embibe.com/study/effect-of-placing-thin-transparent-film-in-ydse-in-front-of-slits-concept

Consider the experimental setup for Young's Double Slit Experiment:

Here there is an angle between the directions of propagation of waves ,i.e., $\angle S_1PS_2$ - the angle between the electric and magnetic field vectors at that point other than the phase difference.

My question is:

Why is this angle never taken into account while analysing this experiment or the diffraction experiments?

Source of the image: https://www.embibe.com/study/effect-of-placing-thin-transparent-film-in-ydse-in-front-of-slits-concept