Far better to have a dedicated external-id property for schema.org,
which would avoid this; and if there are important concepts there that
we don't have an item for on Wikidata, then create those items.
Creating a dedicated property for schema.org, would also imply the need for creating designated properties for other context providers such as OBO, SIO, etc. I see that having to filter on matching uri providers in a single property can be complicated, but would that be more complicated than having to consider all possible schema/context providers through distinct properties?