I think he means a web management for hosting a relay.
You may want to do some stuff around safelistjng or block lists or even being able to conveniently manage relay data.
Discussion
Ah ok. For the operators. Gotcha. I run 3 relays. You can do allow/blocklists. Basic Linux commands for editing settings.yaml or whichever the specific relay uses. (I'm using nostream). Easier imo to manage through CLI than GUI
Not to mention that a front-end system just opens up your attack surface for more vulns