In fact old BIOS systems are more resilient. With a separate bootload on another disk, starting from that disk and then chainloading Windows (on another disk) or Linux works very stable as Windows is not trying to change the boot order of BIOS.

But Windows likes to also meddle with UEFI. Even with separate disks each with their own ESP it likes to change you EFI settings to make windows the default again instead of the boot menu on another disk (everything on the same EFI is even worse, because then Windows can access and delete everything now Windows and you have to restore the boot loader/menu).