> With hindsight, we've never really tried to use that flexibility in the real world, but the capability is there if we need it.

Maybe not in public networks, but if you run your own network you can easily make use of auto-subnetting.

e.g. see [0], [1]

[0] https://github.com/RIOT-OS/RIOT/tree/master/examples/gnrc_ne... [1] https://summit.riot-os.org/2021/wp-content/uploads/sites/16/...