It was originally made for the fully sandboxed dual screen Surface Neo (and similar dual screen/foldable devices from other manufacturers). That project failed

It was originally made for the fully sandboxed dual screen Surface Neo (and similar dual screen/foldable devices from other manufacturers). That project failed (because every semi-competent developer at Windows division has either quit or moved to Azure). So they slapped together Windows 11 by merging Windows 10 and the shell from that failed project.