Last time I checked it was not like that - those kits are actually quite easy to use.
The catch is that in order to buy it, you need to give them SN of the device in advance. Meaning you cannot have stock and thus you cannot offer any reasonably fast repair service. And even after that you have to contact their support in order to "pair" the newly installed parts to that device.
Most of the people I know use 3rd party repair shop because they can change battery/screen in 1-2 hours and they will not wipe your data. Apple takes 2 weeks and wipes your phone.