It´s not in the A11 kernel. There´s also no reason to use it, if your phone sleeps just fine.Is the Boeffla wakelock blocker in A11 kernel, too? How to use it if so?
It´s more of a last resort for example, if your companies wifi causes your device to not sleep, due to a wakelock which originates due to your phones wifi driver not playing nicely with the companys wifi network, and your company´s IT-guys refuse to update/solve the issue on their end.
Blocking kernel wakelocks to get "better battery life" is more myth/placebo than anything else and will cause random issues like missed notifications etc.