Myth or Reality: Employers will contact your academic supervisor and past collaborators to acquire information about you

Recently in a presentation about networking the presenter mentioned that it is important to maintain a good relationship with your past academic supervisors and collaborates (teammates) because employers (industry employer, not academic employers) will go contact these people to gain information about you, especially you are a recent grad with net zero industry experience.

Is this a common practice? Does anyone know if employers will actually go out of their way to contact your supervisors even your teammates?