> Punishing in public

The junior dev is watching, and got the benefit of seeing that you value his time

> managing via Slack

Far preferable to arranging a face to face meeting over this low impact, simple procedural issue

> being a speed bump just because

Defending your team's finite attention and time from random direct requests from the business is a major part of your job as an EM.

> "scope creep" bogeyman

There's good reason scopes are defined and communicated, and deadlines and expectations are managed.