If he were covered by FERS alone, he would max out at a lower value but he would have had use of matching funds based on his current salary for use in his Thrift Savings Plan ~ CSRS folks did not receive matching funds.
It's highly complex for folks covered by CSRS, FERS and Social Security ~ and maybe even VA pension plans.
Still, I wouldn't mind having one of those federal gigs - many sound far better than anything I had in the private sector.