> What is an "excuse" for a layoff, exactly?

By "excuses for layoffs" I suspect what they meant was that there was an pre-existing desire to reduce headcount and RTO was used under the expectation that some percentage of employees would quit voluntarily so that the company can avoid going through the relatively more costly process of laying them off.

Of course the downside of this approach is that the company has less control over which employees leave, which may result in them losing the employees who have the best alternatives.