"this thicket of qualifications and corollaries"

Thicket; nice folk word Pip.

"It is self-conscious second generation performance revival folk with Prog Rock sensibilities but contains all the audible ingredients that mark it out as folkish."

Try the easy version then: "self-conscious".

All modern performances of folk, traditional or in-the-style-off are one would hope, self-conscious. Unless you believe dangling a leather tankard and hooting 'as I roved out' means you've done any actual roving lately or the pub ran out of glasses.

"second generation"

The Unthank girls family 'tradition' is the folk revival, especially sea shanties IIRC. They therefore have the sensibilities and material of that revival and being modern geordie lasses, a good ear for pop and rock too. Not Venus from the clamshell perhaps, but a fair chance of doing justice to traditional material.

"prog rock sensibilities"

My guess is progressive and experimental blues rock, to give it a more descriptive title, formed a fair bit of many folkies musical education. Remember we're talking folk revival here, a fashion, a response to the political and social climate of the 50s and 60s, not mainlining tunes heard on mother's knee from her mother's mother. On that basis why not sing Wyatt?

Rather than list which audible ingredients suggest it is folk can you list the musical factors than means it isn't? We're talking things you can hear and repeat remember, not stuff that has to be checked in a library; stuff of the common man and woman not intellectuals, taxonomists or PhD students.