Depends on the "side project'.
Due to the age of AI, I ask it to *everyone*. It is enough to filter in those who would go the extra mile to build high quality and widely used software dependent on by others versus those who just call it a day.
Obviously, I would be interested if it is the following:
* It should not be a hello world project.
* The project solves a problem that is relevant or similar to the job description.
* The company happens to use a critical piece of software that the person is maintaining or has contributed to.
* It makes money.
It's very simple, but the goal is to give an easy reason to the interviewer as to why you are "exceptional" against the competition. We are also in the age where there is rampant title inflation. "Juniors" posing as "Seniors" and vice versa. So weeding them out with extra projects, etc is exactly what I would do.
"Seniority" and work history is just not good enough against 100s of "seniors" or "juniors" in the candidate pipeline.