What’s the collection you pass that Filter over? And how did you construct it? It seems like you’re going about this backwards from how I’d do it. I’d use names(MyPkg) for your starting point — those are the symbols you need, and then you can filter them by exported/public/internal and even further refine them by their value with getproperty(MyPkg, :foo).
You’re just getting “lucky” that named functions know about their names and happen to have a Symbol constructor that gives you that name back. But it’s not even necessarily the exported name from the module.