I don't know if this will help, but see Einhorn v. McCafferty, No. 5:14-cv-06924, United States District Court, E.D. Pennsylvania (March 31, 2016) that you can find at https://scholar.google.com/scholar_case?case=8170636359019689152&q=Einhorn+v.+McCafferty,&hl=en&lr=lang_en&as_sdt=20000006&as_vis=1
In this case the District Court discusses the difference between shared and separate interest allocation of a defined benefit plan, the age 50 rule and the “severed rule.” The Court explained:
“Here, as in Files, the language of the settlement agreement reveals that Kevin intended to afford Deborah a separate interest in fifty percent of his pension, rather than a mere interest in sharing a portion of any benefit payments that he later received. This is a critical difference, because under the shared payment approach, the former spouse receives nothing if the participant does not receive any payments (there would be no payments to split). Kevin died before he began receiving retirement benefits, which means that if Deborah had been given only a shared payment interest, she would not have been entitled to any benefits. But under the separate interest approach, "because the spouses' benefits are independent, neither spouse's benefits stop upon the death of the other." See 2 Brett R. Turner, Equitable Distribution of Property § 6.34 (3d ed.), Westlaw (database updated Nov. 2015) (emphasis omitted).
“However, there may be a problem for Deborah. At the time of Kevin's death, he had not yet reached the minimum age to be eligible to start receiving benefits from the Plan. While a person who is afforded a separate interest in someone else's pension plan is treated like a plan participant in his or her own right, that person nonetheless "cannot . . . receive a benefit earlier than the date on which the participant reaches his or her `earliest retirement age,' unless the plan permits payments at an earlier date." QDROs, supra, at 40. Under the terms of some pension plans, this means that if the participant dies before reaching the minimum retirement age, any person who holds a separate interest in the participant's plan loses that interest. See Raymond S. Dietrich, Qualified Domestic Relations Orders § 10.04[1], Lexis (2015).
“Other pension plans are different. They apply the so-called totally severed approach, which means that when a participant gives another person a separate interest in his or her pension plan, the plan completely separates the two interests, leaving the participant and the beneficiary as two autonomous plan participants. Under these plans,
‘an alternate payee [can] begin receiving her entitlement when the plan participant reaches retirement age, whether the participant actually retires or continues working. If the plan participant dies before retirement, the alternate payee may begin receiving benefits when the participant would have reached retirement age; the participant's death, whether it occurs before or after the participant reaches retirement age, therefore does not affect the alternate payee's entitlement.’
“Krushensky v. Farinas, 189 P.3d 1056, 1062 (Alaska 2008) (citing David Clayton Carrad, The Complete QDRO Handbook 70 (2d ed. 2004)); see Dietrich, supra, § 10.04[1]. This approach fully protects a former spouse who holds a separate interest in a pension against the risk of the participant dying before reaching the minimum retirement age.” You can find Krushensky at https://scholar.google.com/scholar_case?case=12011889634268315346&q="severed"+"separate+interest"+"defined+benefit"&hl=en&lr=lang_en&as_sdt=20000006&as_vis=1.
These are the only two cases I have found in the US discussing the concept of "totally severed" as it applies to QDROs or divorce or "separate interest" or "defined benefit" or subsidy or subsidized. So I suspect the answer to your questions will be found in the language of the QDRO itself, or in State law, or in the Plan documents. I think your Plan Administrator needs something to hang his/her hat on other then his own preference. I don't think the age 50 rule prevented the early retirement subsidy from kicking in. I don't think IRC 417(c) changes that outcome. The benefit never came into existence.