Management is inherently interrupt-driven: phone calls, meetings, other interactions with the organization
Development is generally NOT interrupt-driven; in fact each interruption has a productivity cost. You want your developers 'in the zone' as much as possible. A phone call, a question, a meeting, not only take time in and of themselves, but in the time it takes for the developer to get back in the zone, which could be much longer than the "quick" question you just interrupted them with.
A good manager (technical or otherwise) keeps interruptions away from their developers as much as possible, A non-technical manager MAY be at a disadvantage, if they cannot do their job without a technical 'guide dog'; but if the organization is structured in such a way that technical proficiency is not required (i.e. not expected to estimate tasks or understand or explain the internal workings of a particular subsystem), then they might be able to manage just fine.
So... depends. Duh.