Yeah anything salary-related for FIRE is going to look stupid to us because most of us saved heavily to get to FIRE. Therefore, salary was irrelevant to what we needed to have per year for retirement.
But as mentioned above, these advisers oversimplify way too much with the 80% rule because people don't want to do the trivial task of using a budget to track expenses.
Well except for the author of this article, who uses salary for way-too-complex thinking that pretty much no one will adopt as a method to use. The masses aren't and we aren't.