It's about readability
Do you remember which languages they looked at?
* "Shorter [C#] identifier names take longer to comprehend" (2019) https://link.springer.com/article/10.1007/s10664-018-9621-x
In this paper, we investigate the effect of different identifier naming styles (single letters, abbreviations, and words) on program comprehension. We conducted an experimental study with 72 professional C# developers who had to locate defects in source code snippets. ... We found that word identifiers led to a 19% increase in speed to find defects compared to meaningless single letters and abbreviations, but we did not find a difference between letters and abbreviations.
* "[Java] Identifier length and limited programmer memory" (2009) https://www.sciencedirect.com/science/article/pii/S016764230...
names used in existing production code are long enough to crowd programmer’s short-term memory. This provides evidence that software engineers need to consider shorter, more concise names. As the study considers individual names extracted from production code, it tends to underestimate the demand on memory because there is no need to remember context as well.
* "Evaluation of Rust code verbosity, understandability and complexity" (2021) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7959618/
By most people’s account, the actual coding part of programming isn’t really a majority of their time. Domain research, speccing, debugging, testing, planning, etc. the microscopic savings in key presses are just really such a strange thing to even debate about when you think about it.
Major tersness pushes also tend to cause “symbol soup” and, personally, I find symbol soup very hard to digest.