My Cloud Home - Accessing the Public Space within Home Network (WiFi)

I have a My Cloud Home plugged into the network at home. This NAS was bought to relieve the many cloud solution my wife and I are using and start centralizing some of our files and pictures.

I’m pleased with the separate environments and a shared folder in our online environment. I however notice that while at home, browsing pictures is a tad slow. After reading into some earlier questions and articles - am I correct in understanding that when I am using this drive from home - on the same network as the drive is plugged into - all files I open are still being uploaded and downloaded via the WAN network? (eg: via WD servers?)