Trump isn't alone misunderstanding or misrepresenting the issue. Some people are ignorant; some are misstating the situation for effect. I've already stated the truth of what is happening. "It's a lie that babies are being killed; they are being left to die" isn't a good message for swaying voters. People who have got their teeth into that one are preventing it from dropping into the memory hole; as long as it's talked about, the reality is in the public mind along with the lie.
Abortion is maybe in the bottom 3 of the top 10 issues right now. Democrats are eager to run on it, and specifically on permissive federal legislation. I read a claim that the debate spent almost 30 minutes all up on abortion - one third of the available time. The average American position is restrictions after about the first trimester, with the usual compassionate exemptions. I doubt her position helps Harris.
I admit it's kind of weird that a politician would lie about something, or state that someone has a position they either don't hold or have denied holding. I suppose now that fence has been breached, we'll see more of it.