Thank you. I did solve it already with a SetWidget. I was hoping for a solution that would use the LetWidget as is.
Essentially I am wondering if the LetWidget is limited to filter results with only one returned title.
Thank you so much for your help, Mario!
This conversation did kick a cog into gear in my head and I realized that the filtered transclusion was returning a list and that is distinct from a string with spaces. so I added a +[join[ ]] to my expression and that got me the result I wanted.