After rolling it out and enjoying this for ourselves as we handle our own customer support using our own software, it's become a "why didn't we do this earlier?" type of thing.
Overall, there's already a ton of asymmetry of information when a customer contacts a support team (e.g. our product pulls in order history, subscription details, stripe transactions, etc) that streaming a text preview is really just a drop in the bucket, and it's actually a win-win for both sides since it leads to faster answers.
Also keep in mind that any questions you ask may be used to feed machine-learning systems, like chatbots, which is true for our product as well. Just something to be aware of, that I think is a fair tradeoff for better customer experiences long-term.
Disclaimer: I'm the founder of https://reamaze.com