Yes, exactly. Strange experienced a course of events, changed time, and set forth a completely new set of events. That is a new timeline. A completely new set of events. The main difference between what Strange did and what Avengers did is that instead of moving himself through time, Strange moved time around himself. (And yes, a whole plethera of other differences). I agree that the way he did it made the timeline where Dormammu invaded cease to exist completely, but it was still a separate timeline. A separate series of events.

I dont understand how a completly new series of events in time created via time manipulation is somehow also not a new series of events. If I walk down street A, rewind time, and then choose to walk down street B, i have created a new timeline. Strange Saw Dorm invade, he rewound time, and caused Dorms invasion to have never taken place. Thats a new timeline. Theres one where he did invade, and one where he didnt. To me, that sounds like two different series of events.