Out of curiosity, what are you trying to do? My project that’s driving this component is also sort of a terrain system.
The static mesh doesn’t have adjacency stored, it’s just transient information needed to calculate smooth normals (and actually tessellation as well). The SMC has all of the normals/tangents/tessellation information calculated at cook time in editor so it doesn’t have that information by runtime.
You do pose an interesting question though and it’s definitely possible to setup the normals/tangents calculator to use a stored adjacency. Could either do a separate helper to get the info, and you just feed that to the normal calculator each time you need to recalculate. About to start into tessellation and I know the adjacency is needed for that so might be useful for more than one thing. Actually if I’m going down that path I could even easily make it so that you could build the adjacency info yourself since for many things (like heightmap terrains which are a giant grid) it would be faster to generate that info yourself during mesh generation than to have a general purpose function find them afterwards. (I’m not saying only supporting you supplying the info, more that you have the option to if you can do it faster)
Once you have adjacency then calculating normal/tangents should be pretty quick. What size meshes are you using? Also, if it’s just a plane, why are you using SMC conversions?