Newer efforts like (replacing UEFI firmware with Linux kernel) may integrate Win2Grub-like functionality at an even lower level.
To understand the necessity of Win2Grub, one must first understand the mechanics of how a computer starts. When a PC is powered on, the BIOS (Basic Input/Output System) performs a Power-On Self-Test (POST). Following this, the BIOS looks for a specific location on the boot drive: the Master Boot Record (MBR). win2grub