You can change which monitor is primary if you wish in Windows which would seem to achieve what you want.
Moving your primary taskbar to a non primary monitor is extremely edge case which is probably why Microsoft have removed this from Windows 11.
I cannot say if we will or will not be offering this in a future Start11 build as it is fairly low down the priority list.
That said I believe future Win11 builds are improving the secondary taskbar to make the primary and secondary taskbars more feature equivalent (adding in the clock and I would expect to see more) which makes sense as there is no reason why they should not have been identical on Win11.
