Spatial coverage is specified in a variety of ways - e.g., geometries (bounding boxes), country codes, geographical names - which are usually domain-dependent. This prevents interoperability, but it is on the other side unfeasible to force the use of a single approach, since (a) this might go against existing standards and (b) a given approach may not be suitable to model the notion of location of given domains.
DCAT-AP rightly adopted a flexible approach, recommending the use of the Core Location vocabulary, and not formally excluding a priori any of the common practices. However, it might be useful to complement this with a number of best practices, that, e.g., may correspond to the different ways spatial coverage is specified in the relevant metadata standards (e.g., typically, geospatial metadata use bounding boxes, and statistical metadata NUTS).
This would be an opportunity to extend the harmonisation (and possibly interoperability) of spatial coverage.
Recommend best practice for spatial coverage.