Loft Distribute UVs Between Edges or UVs

Default Options

With the default options, "Loft Distribute UVs Between Edges or UVs" will distribute UVs sandwiched between your selected edges and/or UVs along a (dynamically created and not retained)loofted NURBS surface created from the UVs and/or edges you've selected:

Proportional Distribution

The default distribution type for this tool is "Uniform", however you can select "Proportional" distribution in order to distribute UVs with spacing relative to their distribution in 3d space: