It should be done if the relation is too large and a super-relation is a replacement, at least that is what the guidelines are saying. Again anyhow, it is just a guess. You have edited the two cycling relations before so perhaps you'd know why they are tagged as they are now.

All in all a networked route (with multiple interconnected highway=cycleway connected into one osm.wiki/Tag%3Aroute%3Dbicycle) may not be the norm outside Asia but it happens for reasons (one of which I think is for saving server resources). It is not breaching the guidelines and the flexibility is there for region-specific situations so as long it is conforming the major guidance applicable across OSM. If we are able to reach a consensus in the mapping community that this should be transformed into a Relation:route_master instead then we could do so.

(For your 2.2, I am well aware of it and thus I have raised in a "strictly speaking" matter should we decide to dwell into such precision on directionality)

i. We would have been able to comprehend your interpretation better had you underpinned that "most" of the walking routes in OSM is located in rural area, or that walking routes should comprise "mostly" rural sections.

Assuming that you have meant the latter one (otherwise my example still stands valid), it would have been the best if the unspoken rules are codified into tagging guidelines/conventions as what other OSM communities have done upon reaching a consensus (say, differences compared to route=hiking). By such, experienced editors such as you and newbies like me could follow better. I am sure some of the discussions in this thread, also seemingly not explicitly detailed in the guidelines such as the naming convention, are also worthy of being listed in the respective guidelines.

ii. for example, two bicycle routes relation/10553685 and relation/10619470 are both grouped region-wise without a clear main direction. Strictly speaking, some of the route=ferry do not contain separate forward & backward relations as route=bus and route=road does. If there has to be a clear to-fro mark for all relations, then we will have to take care for all of these as well.

A random search lands me at relation/1623950, an urban walking route tagged with route=hiking. "Mostly rural" I imagine is not exclusive?