If a user has a disk over 2 TB in size and tries to install to it, with an amd64 version of a 12.1 release at least, when it comes time to partition the disk, the installer selects dos. If a user proceeds with this, then the system will only use 2TB of the disk, whereas if the installer detected this and selected gpt, then if that is used, the entire disk will be seen.
The installer should probably select GPT universally these days.