EPSG:4326 is a geodetic CRS, so it's not a projection. That said, a lot of people seem to use it as if it were, so it makes sense to support that.

Perhaps more importantly, I'd want to check how axis order interacts with the extents. For example, EPSG:4326 is specified as lat-lon (i.e. YX), but something like EPSG:27700 is specified as easting-northing (i.e. XY).