Traits redux

[JN via Digitalmars-d-learn]

https://run.dlang.io/gist/ec7008372d60ac52460dd58068f1ca6d?compiler=dmd
Why only listUDA2 works and listUDA doesn't? Why do I need to use 
__traits(getMember again, if I use what I saved in a variable, it 
doesn't work :(