As kj has pointed out, "Shared Facts" in FTM only has to do with facts to be shared with both a husband and wife.
For right now, you can "jerry-rig" shared facts by a shared source or source citation. For example, you can see all members of a family in a post-1880 census record by looking in the Source Workspace, selecting the source, then the citation, and see the people in that house attached at the bottom of the middle pane.
But all of the facts associated with that census record are still individual instances of individual facts.
Although changing the structure of FTM to enable a fact to be shared, and even have roles (like in a will: maker, executor, witness, legatee, named in property description, wife, son, daughter, grandchild, nephew, niece) would be nice - I doubt if it will ever be done. Now that FTM is "locked" into ancestry trees formats, they would have to change the structure of both at the same time. I may be wrong, but I don't see that happening. I think the "die is cast" on this issue.