Cannot enable dynamic classpath in 2024.3

Regardless of what I try (@argfile in Run/Debug configuration, dynamic.classpath:true  in workspace.xml), I cannot convince IntelliJ to run with a dynamic classpath.  When I upgraded from 2024.1. to 2024.3, I actually saw a single run that looked like it contained a classpath file prepended by @; but no longer.

What's the trick in getting IntelliJ to use dynamic classpaths? This seems to be an ongoing issue for at least 8 years based on SO posts I've been reading.