No level of service is guaranteed, nor is there any guarantee that there will never be any issue. There's no law that says the service has to work 100% of the time for you to be able to use VOIP service in an emergency. You might be thinking cell phones allowing you to make a 911 call even if you don't have current cell service through a company.
The speed testing is done to both demonstrate the issue, and to help give info that can point them in the right direction of the cause. It's a part of the initial troubleshooting.
With this said, it appears that Remy is already working with you. However, if your phone is reliant on the service, so you're not able to get the call you're expecting, I'd mention that, or even reach out to Remy via the private message he sent you.