What kind of "should" is that?
The first post in this thread details the release notes. Nothing in them entails any of your claims. In fact, at least as of 17.9.3 autosteer is clearly now also using cars to track lanes in absence of lane lines themselves. It's done this for me to get through intersections. Even more, autosteer can work with a single lane determination, e.g. in the case of no middle line but with a solid curb on the other side.
So, I mean, yeah, I concede the point that you personally wouldn't use autosteer in an intersection and you advise others to do the same.
But that's not because of anything Tesla tells us. And it's not because all autosteer does is read lane lines.
Can we coin the term: Elonians? Like Straussians, they see subtext and get meaning from extra-textual clues and hints. Nothing actually said can be used to prove that an Elonian interpretation is wrong, for that very wrongness reveals the rightness of what the Elonian is saying.