Can't use the word "buy" if you can't actually buy the thing.
The data on that is worthless with online DRM, and I'd bet that GTA 6 would require online activation regardless. The real enemy is DRM, disks being gone is just a symptom.
Games have also always been tied to licenses, the details are what matters really. A license to use a program that can no longer launch because a server is down isn't any more useful if you have the program on a disk.