fast boot is on in windows 11.
when shut down and then start windows 11, or reboot windows, it will resume last state when fast boot is on.
So if memory usage was high in last state, your memory usage will still be high even if you reboot and with almost no app opened.
search online on how to turn off fast boot.
with fast boot off, you can allievate high memory usage situation by reboot.
but there is definitely a bug in windows 11 thats causing memory leak continuously. unfortunately, we can't fix it by using other diagnose apps, such as RAMmap. We can only go around it.