I haven't seen the article, but I have read the book. So, I'd say that the difference that makes a difference, between imaginary snakes and real snakes, is the practical distinction between Concrete and Abstract. Concrete things have physical properties, such as poison, that can have physical effects, such as death-by-snake-bite. But Abstract things, have their physical properties abstracted (pulled out), so what remains are ethereal meta-physical qualities (MPQ). MPQ are not inherent in snakes, but attributed by the observer. And one of the MPQ of both snakes-in-the-flesh and snakes-in-the-mind is that they can cause the real physical responses we call "fear". You may mistake a garden hose for a snake, but the fear-response will be the same. And some people have dropped dead from fear --- yet the cause was not bio-chemical toxin, but bio-mental shock.
If the mere idea of a snake can kill you, it's not due to what-is, but to what-seems. And what "seems to be" is important to humans, because we are motivated by feelings. Moreover, some of those feelings are pre-suppositions (beliefs) about what's real and/or important. Some of those suppositions are innate (learned by evolution), or empirical (learned by experience), but others may be superstitions (learned by education). But the emotional effect on the believer is real, whether triggered by "what-is" or by "what-seems" (physical or metaphysical). Yet, some of us belittle Meta-physics as not-real, even when such ideas have real-world consequences. For example, world-wars have killed millions for the sake of abstract ideas (Communism vs Capitalism), that are only indirectly connected to the real world. However, going to war over mere ideas may sound silly, so those who want to justify the physical effects of war (carnage) typically look for some real-world event to blame. Even when the "real" motivating reason is an abstraction like "honor", or "freedom", or "country".
The abstract difference that makes a difference is Subjective Meaning.
https://www.britannica.com/story/can-yo ... d-to-death