Prime rate may be for banks "best customers" only, and indeed "very rare". But what does a bank charge for a loan FULLY SECURED by the balance of a savings account held at that bank? This is akin to what a plan loan is like, the plan has NO RISK, just like the bank making a passbook secured loan has no risk. Prime+2 seems high.
masteff's observation is apt for many reasons. Among them is respecting the participant's privacy. It's at least possible that a participant might not have wanted anyone other than the beneficiary to know whom she named as her beneficiary. Or if she did want others to know, it was for her to choose to whom and what she would reveal.
An example of why it should be avoided for anyone who is not the listed beneficiary to know who was listed as a beneficiary. Now you're caught in the middle of a squabble.