Part 2: missing capability of reporting collection extent in a non CRS84-CRS
Part 1 has a provision, in the /collection response, for a extent.spatial.crs member. In Part 1, it is optional and, if specified, restricted to CRS84 / CRS84h. Part 2 doesn't unlock that restriction to other CRS. Ideally we'd also want to be able to specify the spatial extent in multiple CRSs, because reprojection of the bounding box expressed in one CRS to another one might add significant "padding". e.g from CRS84 to a projected nativeCRS, when the area of interest is at high latitudes
In OGC API - Maps (Coverages TODO), we defined "storageCrsExtent" (in addition to the WGS84 extent):
https://github.com/opengeospatial/ogcapi-maps/issues/45#issuecomment-1326751913
See also http://docs.ogc.org/DRAFTS/20-058.html Requirement 46 D and Example 8.