But he has indicated that he wants to go fly in the US so a FSDO is probably his best bet and yes, he does need his license to be validated by CAA per the link I posted. He could use a European DPE but is probably going to find it a lot easier to do it in the US. I was just pointing out that it is not quite so easy and straightforward as you made out, particularly if he doesn't happen to be in the Sunshine State.
You may assert the BFR/Medical business,and I'd agree with you on the letter of the FAR's however my own flight school in the US is happy with my UK license and medical backed up by the 61.75. It's clear that the FAA's intention is that the 61.75 renders valid (in the ICAO SARPS sense of the term) the foreign license.
Oh and by the way, if he were to decide to get an FAA standalone he'd need TSA approval, fingerprints and all the rest of the malarkey, even though he's transitioning from one PPL to another and not extending his privileges.
I'm in the interesting position of having my 61.75 based on a CAA lifetime PPL so where does that leave me? I won't be able to fly an "EASA" aircraft in Europe, but it's an ICAO license that entitles me to fly one elsewhere. I can of course pay 45 quid to get a LAPL which will give me back the privileges they intend to take away. Hmmm..... now what does the S in EASA stand for?