because this value already has been deleted. That’s why it doesn’t appear.
here some examples
disable value(same effect):
bcdedit /set useplatformclock false
delete value:
bcdedit /deletevalue useplatformclock
enable value:
bcdedit /set useplatformclock true
edit:
don’t forget to restart your system after change value.
for me, this increases performance but I still suffer up to 15 fps drops when fx renders.
value enabled = 17-20 fps (with vapour effects seen = 7-10fps)
value disabled = 50-55 fps (with vapour effects seen = 37-42 fps)