This is definately a show stopper for some designers. If your workflow requires building/editing symbols in context, this will definately suck. It should probably be heavily noted that this is the case to warn teams that require building their symbols in context.
For workflows that build symbols out of context (e.g. Atomic or other modular based workflows), this is a non-issue and would actually help to force symbol agnosticism to build symbols that work for multiple contexts rather than one.
However, I can see the need to adopt and interface where the user can choose to edit in context or go to the Symbols page (e.g. Adobe Flash movie clips).