As a freestyle job at top level (not under any folder),
the groovy script below is working
for both "Active Choice Parameter" and "Active Choices Reactive Parameter":

return [ jenkinsProject.getName() ]

But when I move this same freestyle job under a "Cloudbees Folder",
or when I use the same script in "Multibranch-MultiConfiguration" job
then it will run the "Fallback script".