Im going to go on a limb and assume that since BHVR can provide perk and killrate statistics they could easily just create their own statistics website/Information center Tab that pulls the data from whatever database they have and show it to us with regional/MMR data filters included.
Would help include non-pc players aswell as provide better insight to the community into true usage statistics, until then, nightlight is the best we have.
It is not and thats not "killersided"
We know from BHVRs official statsitics that BHVR is trying to balance on a 60% winrate (over all maps and killers and MMR rates). In that logic every Map with under 60% winrate for killer is "weak" for killer and every map over 60% killrate is "strong" for killers.
Nightlight doesnt have all data, because not everybody is uploading or even know about that side. But since Nightlight is all we have when it comes to statisticits its still good.
But you should be aware that not all people know or use the side to upload their games, so its not 100% true. I also dont know how nightlight avoid doublegames
For all the caveats that come with looking at nightlight for stats.... Game and RPD are usually killersided (as others have already pointed out ^^)
The only killers these maps don't explicitly favour are M1 killers with no mobility of some sort and no means to take pallets out of the equation (which can be breaking them, ignoring them or blocking them). And all things considered, those are very few (even the poster boy Trapper won't be a part of that group anymore when the midchapter goes live).