That is not what I recall. Do you have any article from Misko & others explaining that? Because what I remember from those days, and what I talked with them, is that they wanted to change how AngularJS compiled directives and solve some ambiguities. They did not even have used Typescript in the first stages. They had their own compiler. The objective was to create a new version of Angular with all the benefits from React, including component compile in build time. They added directives and types to their compiler so they could manage Javascript code like Java Spring code. In fact, they were responsible for introducing Annotations to Typescript. The whole point of using Typescript was useless without Annotations.
See: https://youtu.be/r1A1VR0ibIQ?t=1635