Yeah, look at Windows 10 if you want to see how this can be done poorly. Its boot menu works by booting Windows 10 first and then restarting the computer if you choose another OS. This includes going all the way through POST again. Took something like two minutes end-to-end to get to Windows 7.
Not sure, there might have been a fast path if you were booting to another Windows 10 install. The old legacy Windows Boot Manager also doesn't have the issue since it's much simpler and it executes in faux text mode before the OS boots.
If you Bcdedit, that is known as "Standard" bootmenupolicy, which is touch-screen compatible and it has to reboot in order to reach an alternative OS selection other than the current bootmgr default.
If you bcdedit to be "Legacy" bootmenupolicy, you can select any OS from its simple non-touch text-based NT6 multiboot menu and it will boot right away without need for repost.
