For corporate networks, where you control what devices get onto non-guest VLANs/subnets, you'll have better control over devices that support this new functionality. See for example Google's work on removing IPv4 on corporate networks:
* https://www.youtube.com/watch?v=UTRsi6mbAWM
Even in organizations where IT cannot control devices, like universities which are largely student-BYOD, IPv6 take-up can reach 80%:
* https://www.youtube.com/watch?v=2B-liebzcOMmkm&t=10m
"Obviously" in what way?
But why is this little hack advantageous over dual-stack? Advanced switches already don't forward ARPs they can handle locally.
Because dual-stack means having to deal with stand up IPv4, which entails more configuration, more address planning, more infra, etc. See perhaps "§5.1 IPv6-only Compared to Dual-Stack":
* https://datatracker.ietf.org/doc/html/draft-ietf-v6ops-6mops
Fewer IPv4 deployed subnets means those addresses can be used where they're 'really' needed instead of being 'wasted'.
I don't get your question?
If you use a /32 then there is no broadcast address and no ARP. And the /32 are then announced by your internal routing protocol.