While I agree with you that it should be an option to turn it off, who is telling you that you need to send a full message if someone sees you were typing?

We’re the ones making the rules for this world full of technologies and we create the social rules for them daily with our own actions. Fuck that expectation, I’m sure other people can surmise what happened even if they noticed you were typing for just a second, they’re working with the same limited software.