Based on my samples, sapwood adds complex rich top notes at the expense of longevity and that classic rich deep fuzz and long dry woody tail. I actually have a couple of oils that were extracted 100% from the low oil shavings surrounding the heartwood. quite nice in their own way, but could not substitute for heartwood oil in a blend without many changes
This is a useful reference point. One of my working hypotheses is that inclusion of sapwood in the distillation introduces the foul note I wrote about above. But based on your experience it doesn't sound like sapwood introduces any foul odors at all. If anything maybe there's a golden ratio where some percentage of sapwood should be included with mainly heartwood in the distillation where it would add its benefits without incurring too great a cost to the depth and tail of the oil.
The other hypotheses I'm thinking about (which are surely obvious to you) to determine the origin of this distracting note i keep bringing up, are hydro vs steam distillation, and copper vs steel pots.
The best data I have to go on are from the selection of pure sandalwood oils I have from Aroma Sublime, of which I have at least sample sizes of the oils listed:
Golden Bough, Golden Lotus, White Palace--these were all slow-distilled in-house using copper and glass from the same source material. All great oils without any deleterious aromas.
Zen One--also slow distilled using copper and glass, in-house, great oil with no distractions other than the unique cedar note and I don't consider that a distraction.
Zen Heart--slow distilled using steel and glass, distilled by Pierre but in Japan rather than Vietnam. Same source material as Zen One but the roots were included. Also a great oil with a wonderful cedar aura. Description says distilled in "steel" not "stainless steel" maybe that's simply a word omission.
Samvadita Mysore 2023--Aroma sublime did not distill this oil. The description says trusted private artisan, distilled in stainless steel and glass. This oil to me does have the deleterious note, but its not as intense as other examples I have and has enough of the pleasant top notes to balance it somewhat.
Government 1965--Factory oil, so I assume steam distillation? Definitely has the deleterious note. It's overpowering.
My apologies for charting all this out in long-text form. The reason I am going on about 'this one deleterious note' is because my hunch is that it is either foreign to the material itself or it is from material much too young to produce a quality oil and that there's large quantities of sandalwood oil out there where the source material has been essentially wasted to produce stinky oil. So i imagine there's kilos and kilos of oil being continuously produced around the world using a limited and precious resource being done by people who don't know what they are doing, or who are using subpar or incorrect methods and equipment, or immature trees, or some other unknown to me factor.
Another possibility that i need to consider is that the aroma i have labelled as "deleterious" or "a distraction" is actually enjoyed by other people and my own perception of it is at fault. But then again all the best oils don't have it. And if it is the case that trees not yet mature enough are being harvested and is the reason for the funky smell to a lot of these oils, then it seems there's a lot of deception in the industry.
Another thought i have, is there such a thing as a second distillation using spent material? Sort of like second-pressings of olive oil. Does the government factory do second distillations? Maybe labelled and sold as a different grade than the premium, then decanted (maybe blended with better oil) then resold as a "premium artisan slow distillation mysore". I have no idea what a second distillation with spent material would do to the aroma of the resulting oil.