When a problem arises in windows, the same people that never opened a cmd would be equally puzzled about how to solve the issue when something breaks.
I'm my opinion and experience, great majority of users don't have the skills to solve common issues on windows either. Cue all the jokes and memes from the tech savvy family members that have to fix uncle Lou infested pc.
Maybe we are talking about tradition. People are used to windows, the hardware companies works with them. The pc stores had been selling pre installed windows on pcs for decades. Software and games are being made for windows. People know it's ~~not a good~~ garbage OS, but you have to fight so many walls that the common user is never going to make the jump by himself.
Please use different disks for each OS, you'll save a lot of time and trouble later. It can be done, sure, but you're setting yourself for a world of trouble in the future.
Just a recent issue
https://www.guru3d.com/story/dualboot-linux-systems-affected-by-grub-sbat-policy-changes-due-to-windows-update/