https://github.com/aidancbrady/Mekanism/blob/89e10b1d9d0399ca821c30db3f416638522ee723/src/main/java/mekanism/common/frequency/FrequencyManager.java#L121

This is seeing if a UUID equals a String, which will always be false, since they're different types. That leads to this whole method effectively becoming a no-op. (I'm not sure whether user is supposed to be a UUID, or if it should be checking iterFreq.name instead of iterFreq.ownerUUID, and I can't find the code that calls this method to check there.)

Yeah looks like an oversight. IDEA agrees that it's unused.

That method could probably be removed. Some parts of the code are in need of "some" cleanup