It's weird to see this presented as some sort of novel idea, given that using the same partition for Linux and Windows (and DOS) is how I first ran Linux, more

It's weird to see this presented as some sort of novel idea, given that using the same partition for Linux and Windows (and DOS) is how I first ran Linux, more than two decades ago. IIRC, it was even an option on the Linux installer, and no special setup was necessary (and it was one of the most popular distributions, Slackware, not some weird specialist distribution). All the Linux files were on a subdirectory of the FAT filesystem (IIRC C:\LINUX), and the rest of the FAT filesystem appeared as a subdirectory of the root while running Linux (IIRC /dos). The bootloader was a normal DOS executable (LOADLIN.EXE), which could be started through a normal DOS batch file. The Linux filesystem permissions were kept as special files on each directory (visible when running DOS, but hidden by the UMSDOS filesystem when running Linux). It worked perfectly, and is the reason I ended up on Linux instead of one of the BSDs (which would have required me to reformat to carve out a dedicated partition).