No, it's not. BIOS supports LBA48 for a _long_ time now (which can address a couple of PB).
The main issue is the MBR format which doesn't allow >2TB easily (there are hacks, but those break with older systems).
It would be perfectly possible to teach BIOS GPT, and use the boot sector of the system partition for booting (ie. what happens today).
2TB disks are just the excuse to finally force the issue (after about 10 years of promoting EFI without much success).
The main issue is the MBR format which doesn't allow >2TB easily (there are hacks, but those break with older systems). It would be perfectly possible to teach BIOS GPT, and use the boot sector of the system partition for booting (ie. what happens today).
2TB disks are just the excuse to finally force the issue (after about 10 years of promoting EFI without much success).