Sorry, but an erroneous, uninformed conclusion that's then "defended" by repetitious declarations demonstrating strength of belief is as absurd with pipes as it is anything else.
"I saw an light in the sky! Aliens from Eridanus IV are coming to kill us all!"
Um, no.
And repeating it does not make it so.
Since you planned on retiring the pipe anyway, saw the bowl in half. Side-to-side, axially, it doesn't matter. Then post a pic of the pieces. The wood will show darkening for a couple millimeters around the chamber wall, and otherwise will look entirely new and untouched. Guaranteed.
Briar does NOT split from "absorbing tars and juices" and turn uniformly black from heavy smoking.
If I did, I believe I’d find only a sandwich of tars that soaked inside the briar and destroyed it’s vitality on the inside and the out. In the center, the briar would still look fresh and brown.
The same phenomena occurs in meerschaum pipes, accelerated by using beeswax to seal the exterior.
Only, the boiled and dried, and preferably aged, burls of the roots of heath trees grown around the rim on the Mediterranean are useful for smoking tobacco. There is no other wood as useful, although men have tried every root and wood under the sun as a cheaper replacement.
I believe the reason we must rest our pipes between smokes, has to do with the porosity of briar.
I believe the reason I own over two hundred briar pipes and not one smokes exactly just the same, is due to the flavor of the briar being imparted to the smoke.
I’ve believed all this for nearly sixty years, since Harry Hosterman philosophized about the mysteries of briar while squatted under an oak tree in front of my father’s milk barn.
I can even remember asking him why, and his answer was the same reason there were over twenty kinds of oak trees in Spout Spring Hollow, and only a white oak could be useful for making bourbon whiskey barrels, none other.
Harry thought briar was God’s gift to pipe smokers, and as I get older, that’s the only explanation that explains it all.