`interpolation_mode` parameter needs clarification (9.2)

[tsmbland]

The example settings file in 9.2 gives interpolation_mode = 'Active' as the default, but the meaning of this isn't explained. Instead, the documentation for interpolation_mode further down the page gives a load of other options (linear, nearest, cubic etc.), but no "Active" option.

• What is the meaning of interpolation_mode = 'Active'? What interpolation type is used in this case?
• Other parts of the documentation say: "Interpolation is activated only if the feature interpolation_mode = 'Active' is defined in the TOML file.". In which case, what happens if you use another option such as linear or cubic? Are these redundant/legacy?