I must admit having been in Feng Shui for decades, I have not come across this concept before. It is not one that I have seen anywhere in Asia until now, and certainly not one that I use.
If I stretch my imagination, I can see why they would think three levels might be auspicious, as the ancient symbols called Trigrams signify the relationship respectively between Earth, Mankind, and Heaven. Whilst burying part of the earth level would provide grounding, with a strong connection to nature as well as fate. Yet, we are just about to start a new cycle where both the 4th and 9th levels will be the most auspicious, so it’s a shame that they didn’t allow for that and make it future proof.
Three levels support the wood element and intensifies a clash between the building’s main materials; that of wooden cantilevers with exposed steel, which could get worse over time. However, glass can represent the balancing element of water, and this has been used extensively throughout the structure. No doubt to allow more light in as well as admire the lake immediately outside. We wish the occupants well in their new home.