Yeah, the docs are outdated (I personally never rely on them to learn new stuff, I always search directly on the digests…).
The information on the docs are outdated from before LUF. After they moved to the new LUF coordinate system, many operations changed, but they were not gone, just is used differently, or removed due to duplicate behaviors with other features.
For example, the MakeComponentWiseDeltaRotation function was removed, because that behavior was the same as getting the diference between two rotations, that were already available due to other methods. (Same with other methods such as MakeShortestRotationBetween(RotationA, RotationB) for example)
After LUF, rotations modifications are now applied as operators, for example, the old RotA.RotateBy(RotB) now is made with RotA * RotB (just a multiplication operation).
The same way, the function you want, can now be achieved by RotationA.Invert() * RotationB (get the delta rotation from RotA to RotB, aka the ShortestRotationBetween). Many other operations were removed due to redundancy with other ways of doing it, or had the syntax changed for optimization and better aligning to the verse language design.
And related to the FromXXXX methods, you just looked at the wrong place. All the From/To methods are inside the /UnrealEngine.com/Temporary/SpatialMath module (since they are temporary and supposed to be deprecated/removed in the future). Both the "From XYZ To LUF" and the "From LUF To XYZ" methods, all are there, and not on the /Verse.org/SpatialMath as you assumed initially.
If you find this information useful, please also consider taking a look at this documentation page, it provides extra info about the new LUF system, conversions and usage, and currently has the most updated info that you may need: Left-Up-Forward Coordinate System in Unreal Editor for Fortnite | Fortnite Documentation | Epic Developer Community
