When the taxon split bumps up to common ancestor, users are required to add IDs to specify which output taxon they intended. So adding an Anemone sensu stricto genus ID + explicit disagreement is the way to go – that’s the way to reinstate the disagreement.
It also may help to think of this situation with a different output genus in mind.
ID1: Anemone americana
ID2: Anemone (genus, sensu lato), disagreeing with A. americana b/c, say, the photos don’t show enough details to distinguish from A. acutiloba
----species taxon change and genus taxon split-----
ID1: A. americana --> Hepatica americana
ID2: Anemone sensu lato —> tribe Anemoneae
Now IDer 2 must add their new ID, Hepatica (genus) + explicit disagreement with H. americana.