This longstanding bug also impairs Rhino’s FiletSrf command.
If you want to see how this should work in Rhino you can use this script which can be found here.
The script is designed to work with tangent surfaces so I modified Gijs’ model to make all the surfaces that are being filleted tangent. Tangent_Surfaces.3dm (226.8 KB)
The script works the same as the FilletSrf command. You pick on two surfaces and it will create the fillet between them, but then it also finds all the other tangent fillets that connect to the first fillet and then does the trimming and joining. The fillet radius that will make the spherical corners is 2mm.