@freya I know you are trying to make the most of this for you and other power users, however I just wish to add that not all the blind users are so hooked up to eloquence TTS and only a few of them can use their TTS at such high speech rates. I have understood with this initial version of Graphene Speech services we can at least independently pass the initial setup of @GrapheneOS and then we can switch to our TTS synthesizer of choice. For example I am very unlikely to stop using #RHVoice and you are very unlikely to stop using #Eloquence no matter what do the Graphene OS folks implement.
Having really good modern open-source natural sounding TTS for reading books is not a waste as you are pointing out especially if they are planning to make the other direction part of the app i.e. speech to text as well.

We have the same thing with #NVDA on windows. By default it uses natural sounding voice built into windows that has the same mistakes you are pointing out here, then it has espeak-ng included as an opensource alternative capable of running at very very high speech rates. And you are still adding eloquence into your setup eventhough you need to pass extra hoops in order to even make it run on the modern hardware and software configurations.

It's a very good thing you are advocating for all the blind users here but still if I were you I would try to calm down a bit.