This amounts, in essence, to granting a license to purge civilian populations from any geographical area. Crucially, it employs a very strange definition of "voluntarily." "Your money or your life," says the mugger. I voluntarily (?) refuse to fork over the cash and get shot, but it's okay to kill me because I could have given up the money. That seems wrong.
Similarly, decent people take the view that it's wrong for Hezbollah to take a bunch of basically un-aimable rockets and point them in the direction of Israeli cities and hope they kill some people. Instead of doing that, Hezbollah could
identify some legitimate targets inside the city in question, then state that they'll be targeting those facilities but their rockets have extremely poor aim and so civilians have 48 hours to leave the city, and then start firing the rockets. This alternative procedure would, I think, alter the situation not at all
Again, if the government of Sudan tells the inhabitants of some Darfuri village that they all need to leave in a week or else the janjaweed are going to come in and start killing people, we certaintly wouldn't call that an effort to avoid civilian casualties. Nor would we say that people who "voluntarily" declined to be driven from their homes by threats of force thereby ceased to be civilians.
Similarly, it's surely occurred to most Israelis that one way they could "solve" the Palestinian problem would be to deport or kill the entire Palestinian population of the West Bank. Israel doesn't do this, however, because that would be unambiguously wrong. It wouldn't become less wrong by arguing "there are some terrorists in the West Bank, we aim to kill them all, everyone please relocate east of the Jordan River in 24 hours, anyone left will be considered a terrorist and shot or bombed."
The common thread here is that mass explusion by means of force and the threats of force is the very essence
of wrongfully targeting a civilian population. Rejiggering the exact phrasing of the threat changes nothing.