Who issued the 1099-R? You stated he has lots of things going on. What type of retirement is that from? What about that disability:Temporary disability? Combat? 100% or less?

For military retirement, you first need to know how it is computed.

"If you retired under a disability law (Temporary Disability Retirement List or Permanent Disability Retirement List), your retired pay will be fully non-taxable if your pay is calculated based upon your military (not VA) disability percentage and you meet one of the following conditions"

"The welcome letter you received from DFAS when you first retired indicates whether your pay is computed using your military percentage of disability or your years of service."

From: https://www.dfas.mil/RetiredMilitary/manage/taxes/isittaxable/

And you can read Pub 525: https://www.irs.gov/publications/p525

He might not realize his 1099-R is right, and his friends have different circumstances and codes.