What is the difference between a Network Short cut and a mounted share drive in Windows 10?

Question

I've run into an oddity that I worked around, but can't explain. I'm hoping someone can.

Situation:

I have used the "Add network location" option to connect to an Ubuntu samba shared directory that is 16TB in size. I did this from Computer->Right Click->Add network location and filled in the wizard. I used the UNC path to the share I wanted. This added a folder over a pipe icon to My Computer with the name I provided. For this example, I used \\server1\backup and named it "NAS Backup". There are no quotas on this Ubuntu directory. I have read/write permissions.

I then attempted to copy approximate 40GB of data from Windows 10 to the share by dragging and dropping the directory I wished to copy. After a few seconds, Windows informed me that I was out of space.

I knew I had space, so I tried to mount the path as a drive in Windows. I provided the same UNC path, selected the option to reconnect at login and provided the appropriate credentials. The drive was mapped to Z. This provided a drive over a pipe icon in My Computer.

Dragging and dropping the same directory copied without incident.

My question: What is the difference between these two methods of accessing a remote network location? In both I provided the same UNC path, but with one it informed me I was out of space and the other did not.