TheSpatial Jointool in ArcGIS Pro allows specifying aMatch Optionthat defines how spatial relationships between feature geometries are evaluated. In this scenario, the target and join features are of different geometry types—Points (trees) and Polylines (power lines)—so the appropriate match options are based on proximity rather than containment or other spatial relations.

Within a distance: Matches features based on a planar search radius, ignoring elevation (Z-value), making it ideal for cases where all trees within a certain horizontal distance from power lines should be included, regardless of height.

Within a distance 3D: Includes vertical (Z) differences in the search, which is unnecessary here since tree height shouldn't affect inclusion.

Within Clementini: Refers to a topological boundary relationship and is only valid for comparisons involving polygons—not points vs polylines.

Thus, to includeall trees within a specified horizontal buffer of the power lines, theWithin a distanceoption is the correct one.