The contemporary Japanese methodology of incense culture takes it's roots from the Chinese incense culture. The Chinese have been using some sort of incense as far back as the neolithic period and becoming more wide spread in the Shu'e, Jung, Juo'e Dynasties at around 2000 BC.
The incense culture in Japan only dates back 1200 years, when a Chinese Buddhist monk Jien Jun set out on a mission to Japan to spread Buddhism. He took along with him a large collection of Incense ingredients and Spices amongst other things.
The famous Japanese folk lore of a big chunk of Agarwood washing on the shore and the soldiers burning it for firewood, before the remains were sent to the Palace because the General noted the smell to be beautiful, at the Palace they identifying it as Agarwood. Japanese historians place this event to be after the period that Jien Jun had arrived there and established the understanding of incense, and therefore whilst the common folk had no idea yet (burning agarwood for fire wood) , the nobles were developing understanding of the art.
It is therefore important to understand these arts in the correct context. The Chinese appreciated 3 things in the evaluation of the incense, the ingredients that went into making the incense, the shape /colour of the smoke and how long the smells lasted. They then expressed the evaluation in poetry that was more than just an evaluation but a reflection on life composed as lines about incense. These three distinct elements were observed in three main methods, Indirect heat, direct heat, and Shape burning. Shape burning was the practice of using incense powder and drawing the shape of one Chinese character, then burning it with direct heat.
Across the different Chinese dynasties noblemen, monks and people of the high class were encouraged to engage in incense, painting, tea classification and flower arrangement, these were known as the 4 basic gentle arts.
In the Sung dynasty incense burning was regarded as highly as painting and recitation of poetry. It was studied in the garden or quiet rooms. Guests were encouraged to study the composition of the incense and the shapes of the smoke and the duration of the lingering fragrance. After the appreciation, scholars would express the evaluation in poetry to those present.
In Chinese culture there has been a close affiliation between burning the incense and Buddhism. This is also represented in why there is a focus on sandalwood. The folk of the famous ox head sandalwood is one such indulgence of the period. Incense in Buddhism implies noble virtue and purity. The incense is seen as a means by which one can burn away selfish thoughts.
The Chinese monk took these methods to the Japanese and taught them the same. The Japanese tend to have taken more liking to the indirect method of heating as it aligns with their temperament and also their nature of how they like to listen to the scent. They have to some extent not taken the two direct methods as much, though they do enjoy burning of sticks.
In Islamic culture we have written record of heating of incense that extends 1439years, from there one we have Arabic oral tradition in the form of Poetry that extends back centuries. In Central and South Asia cultures there have both written and oral transmission for the appreciation of incense that extends thousands of years. We have clear instruction on how the incense is applied, the fact that it is not marketed as well as Japanese kodo culture or because majority of Muslims don't know how, does not take from the essence. If we chose to be generous, gracious, hospitable and welcoming by putting a big junk on the ashed charcoal, then that is us saying; my guests I love you so I am going to indulge you with my most valuable possession. and i am not going to be stingy with it.
That same expression to the Japanese might be to do a kodo session, to each there own, but we cant gauge one culture by the standards of another, when the contexts are totally different.
As such to assume that the Japanese are the yard stick for how incense should be heated is very misleading, it is like following the student when there are masters around. But then again that is just a reflection of the whole oudh scene online, everyone has a keyboard and camera to be an expert.