Why would Dunhill wood be so-so? I expect they purchased the best that was available at the time all thoughout the 'golden age' of Dunhill pipemaking (twenties through sixties). Did other makers have superior ways of aging their briar?
I was paraphrasing what these dealers told me, but to be more accurate, one of them said "mediocre". I think they were referring to the quality of grain, and to be fair, grain wasn't that big a deal to most of the British makers as you can't smoke grain. It's nice to look at, but not necessary.
As for processing, that was an area of debate, with some makers stating that oil curing and stoving the wood to speed up the curing process did not replace air curing, which took longer.
Both Barling and Comoy did their own harvesting, curing, cutting, seasoning, etc. In their 1909 (or maybe 1911) catalog, Comoy wrote about their process for curing the wood they harvested through their Algerian operations. I don't know how long they continued to do that. Barling did the same thing, preferring to select their own burls based on their metric for a quality piece of wood, and kept their harvesting operations going, with an interruption during WW2, until 1954, when they were forced to abandon their Algerian operations after Algeria won its independence. After that, they did what the rest did, bought from a broker like Otto Braun.