The solid-from-surface modify item is from ACIS surfaces, which can be curved nurb surfaces, which TC surfaces can't. You can convert a mesh TC surface to a faceted ACIS surface by exploding it to polylines, modify|modify 3D objects|surface|from profile, while they're all selected together, then boolean adding them all together. From there, ACIS surface objects will become volume solids if the surface is watertight, but if it isn't, you get the "all faces are used twice, is this an open shell?" message - with some exceptions. ACIS can cap simple openings to an open shell and convert it to a volume solid without protest, leaving you unaware that that's happened. Solid from TC surface through properties does have a couple of interesting functions, like consolidating coplanar faces into a single face (I know of another program that touts that as a feature for sketchup imports). It also cleans up outlier faces (faces that are only connected to the mesh by one edge), and sometimes SAT healing will work after that's done first, while it fails otherwise. From what I've noticed, that's only with all mesh/facet objects like imported .stls, not nurbs objects with curved faces.
For the record, your original file with 52.5K faces converted to solid in Selection Info in 9 minutes on my i7-7500 tablet with 8Gb, the result with the groove subtracted is 67Mb filesize. I also use a CAD system called PunchCAD, also ACIS kernel, which TC Mac is based on, that limits solidifying mesh objects to no more than 3K faces. It won't even let you slice the .stl up into smaller units.