i have the same issue.
also a geologist and looking to find the intersection of a 3d plane (bedding plane with known dip/strike) with a 3d surface.
why is there no tool for this? it seems like a common geologist problem to extrapolate the expected outcrop of a particular unit?
i can make a 3d polygon, or multipatch polygon from a known outcrop trace.
i have a 3d raster dem, also TIN surface.
i cannot find a tool within ArcPro that can interpolate the intersection betweeen the 2 features.