When tolerances are applied at an assembly level, no transformations that occur on the assembly will be communicated to tolerances or custom features that are owned by the given assembly. This restriction is noticeable when the following two events occur:
Scaling of the assembly: When an assembly is scaled in , each of the bodies within the assembly are individually scaled. This means that assembly level features (like GDT) are not notified that a scale operation has occurred. For GDT, this means that the tolerance zone will not automatically scale by the same factor used to scale the assembly. This situation is not consistent with GDT tolerances attached to parts which are properly notified of scaling events and will update their values should the part be scaled.
Moving/rotating the assembly: When repositioning an assembly, GDT tolerances (and custom features) owned by that assembly are not notified that a transformation has occurred. For GDT, this means that directions (like zone direction) associated with a tolerance will not automatically update when rotating an assembly. This situation is not consistent with GDT tolerances attached to parts which are properly notified of such events and will update their values when parts are repositioned.
The above discussion, in general, applies to all custom features. Should any custom features be created whose owner is an assembly (or more generally, parcels), those features will not be properly notified of transformation events and their internal values will not automatically update. This situation does not apply to custom features attached to bodies. They are properly notified of transformation events and their variable values update automatically when a body is repositioned or scaled.