There is a difference between being able to hear and being able to understand or apprehend what is being uttered by a PSD, as you pointed out to me a few years ago. Not everyone who hears well can understand or has the ability to comprehend what a PSD is saying. Good C.A.s are able to grapple with garbled speech and figure out what word is being spoken. I've been told that STS and TTY Relay C.A.s often have very high, or exceptional linguistic ability. How many people can directly transcribe spoken speech as TTY C.A.s do.
People talk really fast.
TTY C.A.s have to listen, then transcribe verbatim by typing. So they have to be able to type and to transcribe. That is pretty remarkable. If C.A.s start voicing too early, the consumer will be talking at the same time. This is a problem for me because there is a long lag time between the time that my mind triggers the speech and the time that the words come out.