For all intents and purposes, yes. Despite any concern an insured may have with their employer knowing any information about their disability, or concerns over what an employer/former employer might say, understanding your occupational duties is paramount to the claims review process.
Generically, disability insurance policies define Disability to mean (1) a medical condition (2) prevents you from performing the duties of your occupation (or any occupation). This has led to the theory that Diagnosis does not equal Disability. Meaning, just because you have a diagnosed medical condition does not mean you are disabled under the terms of your policy. There has to be a nexus between how your medical condition impacts your ability to work. One of the only ways for an insurance company to determine this is by understanding your job duties and verifying same with the employer. This can often only be done by speaking with your employer.
If you refuse to allow an insurance company to speak with your employer it can adversely affect your claim, including a possible denial of benefits.