I probably shouldn't weigh in because I am still on the fence on the morality of adopting ex-batts (though I admit following yours and Manue's and some others is influencing my thinking on this). But I will anyway.
I think just because you adopt an animal in full knowledge that it will die just as you get to know its name doesn't mean you shouldn't seek professional advice when it is available.
Of course you can only do what you can afford to do but not all veterinary interventions are massively expensive and you can always refuse the more outlandish/expensive tests.
I fully agree that staying with the tribe is important, but in my mind that applies to those situations where people are isolating their ill chicken for a long time - not for the round trip to the vet.
So, I would say, if it is not something Manue and her partner are confident to handle, and they can afford to consult a vet, then why not?
And yes, of course, never consult a useless vet!
I have experienced the 'sure I can euthanize her for you' vet (that was for Maggie nearly two years ago), but even that vet can do a fecal float test for me if I need one.