The wifi battery drain still exist in the official LineageOS 15.1
The number is roughly the same (~4% drain per hour). See my post here:
Although I'm still open whether the problem is from my environment (Wi-Fi settings, being bombarded with other router, etc), or from the LOS base itself.
Some people reported their battery drain is fine, but they haven't told me whether they're seeing the same stuff I'm seeing (WiFi scan pretty frequently)