Its all to do with the beam pattern produced.
It says that fitting them can make the beam pattern blurred and bleed light.
If the beam pattern is crisp, and you pass an MOT, there is no issue.
That artical is also a few years old now (I remember seeing it the first time) and the kits have improved.
If you do fit a kit, best bet is to get it checked with an MOT station to see if the beam pattern is OK