Thanks!
It was coming in hot for 5.4, unsure it would make it even. It will be highlighted in 5.5 officially.
The UV manipulation is a problem only for rect and dir lights which will tile the UV space in the world. And if the UV are not multiples of integer, the tiling will not work (texel missmatch at edges). Same if you use the tiling method on the light itself, that for all the light type I believe. I will clarify that in the documentation, good remark!
As for lumen, thanks for the bug report! I will fix it for 5.5.