If the customer service rep works more hours, at a decreased productivity (tired workers make mistakes, over-stressed workers may be more impatient) such that t

If the customer service rep works more hours, at a decreased productivity (tired workers make mistakes, over-stressed workers may be more impatient) such that the marginal return becomes negative, then YES! it becomes more cost effective to pay someone else to come in on those Fridays. Just like we don't expect those reps to also work evenings and weekends, even if the company has 24/7 support. The article points out some indirect benefits, like improved employee retention, which would decrease training costs and result in more experienced reps working the phone/email, which may improve customer service and relations. This is really hard to promote, which is why there have been experiments along these lines for the last 5-10 years.