Agreed. My daughter is 8 and saves her money for our WDW vacations. Sometimes, she comes home with quite a bit of cash leftover, so putting her money onto a gift card isn't something I'm keen to do. She actually likes being able to open her little handbag and give the cashier her cash for what she's purchasing.
This "test" will probably become the norm across property, so I won't hold my breath over her being able to use cash in WDW in June. But, it is something I'll keep my eye on and plan accordingly once it's all rolled out or whatever. Personally, I think it's dumb.