A very simple reason why oud oil can be sometimes perceived to be more complex than heating wood, nobody can control what goes into the pot or what are the scents of them. It is different from distilling sandalwood, or other coniferous woods where just a single chunk from the tree is sufficient to generate a good amount of oil, for agarwood you need contributions from many parts of a tree, or even contributions from many different trees, and subsequently a possible mix of different species too.
To make things more complicated for agarwood, within the same tree, different parts, different areas have different scent, if you had followed the write up on the age of agarwood resination article.
When heating agarwood, one cannot simply say the complex notes are not there, because some good woods have like 0.1% or less of oil content, you need 1kg to produce 1 ml, and one does not heat 1kg of agarwood at one go either! If you do so, you will have severe olfactory fatique from the intensity.
But if you take this 1kg of raw agarwood, break it down into 10,000 pieces, as 0.1 gram each, and heat each of them in a controlled manner over time, you will discover that the complex/different notes are there, but in different pieces, which is contributed by different parts/species. At 0.1% or less of oil content, at a chemical level that is 500 to 1000 ppm, it is not low nor undetectable in a chemical context. Hydrogen sulfide from rotten eggs can be smelt at a parts per billion level just to show how sensitive the human nose can be.
Not only is oud oil complex because of its contribution from a plural diverse batch of materials from the same region/locus, the processing methods by the distiller, distilling methods etc lend to further changes in the chemical constituents, i.e. oxidation, hydrolysis, enzymatic activity, fermentation etc. Another contribution to why oud oil smells different on different skin (note, smells different, doesnt mean more complex) is due to the different chemistries of everyone’s skin.
What is good/worthy complexity and what isn’t? Perhaps it is good for the consumers to figure out.