I'm pretty sure the necessary credentials are exactly what he showcased -- the ability to write a legible, coherent email in a timely fashion.
As a tech person on the team who would have to help the customer, my first question of the support person would be, "why didn't you gather more information, like the customer's username, error messages he/she saw, browser type and version, etc.?" Not only would that be useful information to help track down the problem, but it would also give the customer some actions to take that would a) potentially lead to a solution, b) make him/her feel like he was actively pushing his problem closer to resolution.
I'm not saying the poster was a bad hire; given that he's risen in the organization and has spent a lot of time there, I assume he quickly learned how HireArt's business works and what questions to ask to get solutions faster for customers... I'm just a little baffled that this work sample got him a job. Presumably it was the process that followed that the founders really liked. Maybe this was just a good filter that easily disqualified resume-spammers and people who can't form sentences.
I think the real value in this post is pointing out something that many recruiters, HR departments, and hiring managers should seriously think about: asking a candidate to solve an actual real-world problem is much more useful than most interview processes.
The "get back to you in an hour" ... not sure about that. You don't want to string someone along with a series of these, and in this artificial case he has no idea exactly how long it'll be before he can get back to the customer. Worse, if enough customers are messed up he'd be sending a lot of identical messages like that out, and for each reply he'd need to make a more personal reply.
The points you make about his interacting with the tech team are well taken, but we might assume the info gathering was already done (ideally there's a ticket system and he could confirm that before sending this sort of reply), and I'm not sure they're relevant for a first level screen like this. If the company has its act together, their next step would be to test all that with some of the people he'd be working together with in the future.
Even if he was powerless to help at that moment, the customer does not want to hear that. The customer wants to believe that they are being helped and that the person on the other end of the line is actively taking steps to get them there.