Why isn’t this a problem with Bounding boxes, and such a fuss-fest here with shrinking ?
I think because bounding boxes are not really ever always on the entire geometry, unless the bounding box is just bounding a box
An why isn’t “ShrinkTrimmedSrfToEdge” accessible in Grasshopper ?
Lots of stuff are not accessible in Rhinocommon or exist as a combination of using multiple methods, it has always been behind Rhino development. But also keep in mind that Rhinocommon is made so devs can use it, maybe some stuff McNeel doesn’t want played with (maybe trade secrets) but more than likely it is just that Rhino develops faster. It could also be that ShrinkTrimmedSrfToEdge is a combination of Rhinocommon methods that are not so obvious to us. The latter is my guess. Just because it is a command in Rhino doesn’t mean it is a single neatly wrapped method in Rhinocommon with the same name, Rhinocommon tends to be a bit deconstructed so it is easier for devs to not be locked into just having the limitations of the Rhino commands, kind of like GH.
Also, you might start a request thread for it to be added to Rhinocommon. Seen that multiple times and they will add it in but it will most likely be added in to a future R6 version (dunno if you are using R5).