If they are using your SSN without your knowledge to get the insurance would be one reason I see.
I don’t the answer to this question but I will put it out there. If my company has insurance on me and I try to get more insurance on myself, would I pay a higher price for being overinsured?
I think once you give your employer your SSN as long as they aren’t actually taking out a line of credit in your name they can just use it.
I’m not sure what guidelines insurance companies use to decide you’re over insured. IMHO as long as you can afford it why should they even care.