Countries are not grouped into tercile groups by all the indicators? Why?

In dashboard 4 on environmental sustainability, countries are not grouped by percentage of total land area under forest, but rather by the change in forest area since 1990. The reason is to respect the fact that the forest area is in a way determined by environmental and climate conditions, while the recent change in forest area is caused by men’s activities. Similarly, in dashboard 5 on socioeconomic sustainability, indicator military expenditure (% of GDP) was not used for grouping of countries, instead the ratio of education and health expenditure to military expenditure was used for grouping and coloring. The reason is that military expenditure was not considered as an indicator in this table, but rather as an auxiliary indicator.