This issue is highly debatable. Someone may urge that technical background is must because they have to have prior knowledge & experience on how handle customers, this is true.
Someone else may urge that the most important aspect or traits in customer service are empathy, humility & good mannerism, the rest are just added advantages, therefore technical background may not be necessary in some customers service jobs.
In a nut shell, since this issue is highly debatable, the outcome of conclusion falls in the beholders hands.