I'm glad you thought the article's explanation was "pretty clear".
For me it was less clear in part because it raised the question: "what is a quantum extremal surface?", which doesn't really seem to be answered in the Quanta article.
Perhaps I could persuade you to try your hand at your terse sort of summary for the interviewee's two-author paper https://arxiv.org/abs/1408.3203 (Engelhardt & Wall, E&W2014) defining quantum extremal surfaces, and having done so return to and similarly summarize the part of the Quanta Magazine article where the interviewee is asked (several years later) about applicability of these defined surfaces outside higher-dimensional anti-de Sitter space supporting a conformal field theory on its timelike (n-1)-spherical boundary, Maldacena-style. (cf. end p.23 E&W2014 and their footnote 6). Such a summary could enlighten one or both of us, and perhaps other readers, and at the very least I'd be grateful (since I have no idea how to capture what quantum extremal surfaces are in only a line of text).
(The open access https://link.springer.com/article/10.1140/epjc/s10052-020-08... is likely to be of some help, its SdS_4 spacetime being a decent approximation of a late-time isolated galaxy cluster in an expanding Robertson-Walker universe. Our standard cosmology models our universe in a way which one might describe reasonably as expanding RW -> dS_4 equipped with a dusty distribution of matter such that at late times most mass -> "dust grains" that resemble SdS's Schwarzschild submanifold. Cf. https://en.wikipedia.org/wiki/De_Sitter%E2%80%93Schwarzschil... ).
