You cant use both partitions

Well you can with a hypervisor, but why bother when you can just run windows VM in linux… until you discover some game anticheats like battleye went out of their way to detect and block virtualization of any kind, so you need to boot windows natively sometimes. Of course you could go the other way and run linux vm inside windows but then all the flexibility of a linux system is lost in a rigid windows wrapper, which makes it kinda pointless…