Developers use software in weird ways. I've written scripts to hit buttons thousands of times for hours on end. It makes sense that they don't want developers' janky experiments polluting data used to drive design decisions.
The label "developer" is relative. Any given product wants to exclude telemetry from developers developing the product itself. There's no need to exclude telemetry from developers using the product like a user. The point is to exclude developers running the software in weird ways to debug it. Not just to exclude anyone that calls themselves a developer.