NPR is targeting ARC, but this is actually a bigger, more difficult problem for the charity industry than one organization not disclosing where it spends its money.
I used to work for a large ($500 million+ annual revenue) NGO fundraising department, both in major gifts and direct response marketing (digital), and I have colleagues who now work for similar organizations (including ARC). We would all tell you that most organizations, even (maybe especially) the largest ones, are absolutely horrible at having any idea whatsoever of the impact of their programs. Even worse, the leadership in these organizations are ambivalent at best at assessing the impact.
Why? Because organizations simply don't have much, if any, incentive to do so. And perhaps more shocking to me, the vast majority of donors don't care. Most people are content to give and reap the warm/fuzzy feeling they get, then not think about it again until year end when taxes are due. Simply put, most people treat giving like buying a product at the store: they hand over money in exchange for the warm and fuzzies. Transaction over.
The people who actually demand some sort of accountability are a minority who are often treated as anti-charity, as in, "Why would we spend money on assessing impact when we can spend that money helping more people?". The result are token 'watch dog' groups like Charity Navigator that latch on to red herrings like 'efficiency' ratings which non-profits have learned to manipulate to the point that they are functionally useless.
ARC is simply the product of a rotten system, and it is far from the only one. If you want to help cure this sickness, only give to organizations that can demonstrate the impact your dollars are having on the cause you care about. Ignore the so-called efficiency splits that say charity Y gives z% of your dollars to programs. These are accounting shenanigans, and nothing more