I have no idea how Blender manages it, but it is the only piece of software I use that has this issue. I have two monitors connected to the one and only GPU in my system, one DP one HDMI, Blender will always, without fail, open on the secondary HDMI monitor. Even more impressive is how this happens not just on Windows, but also on the newest Fedora Linux. It is reproducible with the newest 3.2.2 release from Flathub, the official binary from blender.org as well as the native RPM package, which is quite a bit older.