The taskbar exists in its own timeline, apparently. (Ex-)Microsoft engineers working in the UI/UX team for Windows itself have spoken about how much of a nightmare dealing with that thing was.

Also, the taskbar technically exists as a dll, not an exe, explorer.exe would link to it and run it if it was being ran as the UI shell. This is now split out to its own exe (Shell Experience Host iirc), and explorer.exe is now only File Explorer.

Since it exists as a dll, btw, this is how the Win10 taskbar injectors work, they just call the dll (which still ships in Win11) instead of letting Shell Experience Host do the Win11 thing.

The sane way of handling this, btw, is just use Shell Experience Host injectors to get the desired behaviors, such as using Windhawk and use m417z's taskbar height and icon size plugin (the third most popular Windhawk plugin); to match Vista/7 era small, set to height 32, icon size 16, taskbar button width 28.