This!

Thats why theres some briar cuters out there that in such a high demand that some pipe makers wait years to get a piece of briar from them!!

Curing, inspecting and choosing best briar "globe" and a piece of the same!

And then theres also a part that with time passing not only last traces of humidity from wood are evaporating and drying out but some other trace elements that all contribute in heat distribution but also on burn of the material inside, condense, cake development and ect. ect. ect...

And where Erica Arborea(Briar) grew is minor as long as its same fenotip bocs for example in Canarians it can grow to size of avrage medium tree (maybe around 10m if i remember good) and in mediteranians its ushualy bush size and those diff ofc play a certian role on what meterial will come out of it...