| The system notifies you about software updates from time to time, and you are trained to install them for security. The Big Sur update is notified in the same way. It gives the appearance of being just another big software update. Unlike Windows, Mac OS updates come out more often, about once a year for major version, and every couple of months for minor version. Despite the marketing fanfare, they are not as big a change as say jumping from Windows 7 to Windows 10. Ok, maybe you still want to take care with a new OS. Like with Excel three days before filing taxes. (Though when do you expect the accountant to upgrade? They are always doing someone's taxes.) Maybe you do try it in a VM first, and decide you like it, it works well for you. Some people try new OS versions in a separate partition. You can do that on a Mac, just like on a PC. It seems like it ought to be safe, because you've kept the old installation on as well. Just like on a PC, you can choose which to start up using the built-in boot menu. Being sensible you take a full system backup first. Usually, with Apple, a backup is pretty good. You can reinstall from a backup provided the system can boot. Macs have a reinstaller built in. By analogy with a PC, it's more like "imaging" a Windows or Linux system, and as if the PC BIOS had built-in tools to restore from a backup image. Following that analogy, the problem here is that Big Sur nuked the BIOS! It can't even reboot from external media, or the recovery partition. If a Window OS upgrade did that we'd not only be unhappy, we would also be rather surprised that we can't boot an external USB key to recover. |
Windows 10 has new major releases every 6 months, changes might be more minor than a typical macOS major release. Windows also gets security patches and bug fixes every month, those are comparable to macOS minor versions.