This constraint doesn’t require a distinct type=superroute tag. In OSM XML, a <relation> element contains a full list of its members. Merely by loading the relation itself, the data consumer can distinguish a route from a route of routes by the presence or absence of <member type="relation"> elements within. The constraint you’ve expressed is that the relation shouldn’t have a mix of <member type="relation"> and <member type="way">. The only things the data consumer can’t verify from this element alone are that each member relation is a route relation, and that it’s a superrelation rather than a super-duper relation.
Also, to be clear, various disconnected segments aren’t necessarily a route just because they share a number and network. There’s a U.S. Bicycle Route 230 in both Wisconsin and Ohio, but they are two separate routes, both spurs of USBR 30, with no plans to connect them to each other.