Section 11.5.5.1 Invoking an Action explicitly mentions how If-Match can be used with bound action calls:

To request processing of the action only if the binding parameter value, an entity or collection of entities, is unmodified, the client includes the If-Match header with the latest known ETag value for the entity or collection of entities. The ETag value for a collection as a whole is transported in the ETag header of a collection response.

The same use case applies to bound functions.