You can't call VCO "pro volleyball". It's preparation for pro volleyball but I think Stanford's level is much higher than VCO level...
VCO plays pro volleyball leagues (1. Bundesliga and 2. Bundesliga), which makes it a "pro federal club".
How can you compare playing against MTV Stuttgart, Schweriner or Dresdner with playing teams from universities?
And still, if you cut off VCO, Kastner has been around since 2017. It's pretty obvious she's more experienced and consistent than Gray, which is just playing her first pro season.