may not be able to use this method at all unless I launch the survey into a different browser tab?
The browser behaviour has changed over the years, because security has been tighten everywhere.And it will go on like this.
In the old days the survey was opened via JavaScript fullscreen to ensure focus of the proband.That was misused by advertising, so that the popupcontrol was introduced.
Currently I think the following is still working with uptodate browsers.
If you open a tab/window via _blank (which can be done via a simple link without Javascript involved), you can close that tab via JavaScript.
If you open a tab/window via JavaScript, you can close it via JavaScript.
Browser behaviour changes a lot. E.g. when opening a new tab via _blank, is the browser changing the focus to the new tab or not. Where is the browser adding the tab in the tabbar? At the end or directly behind the parent page? That has an big impact on the survey flow and cannot be controlled by the webpage.