Atreus creator here. It doesn't happen often, but occasionally I have customers run into trouble putting their kit together, and I'm committed to always stepping them thru the process of troubleshooting and walking thru the fix. The last thing I want is for you to buy a keyboard and never get it working properly.
I had the same concern as you, which is why I ordered a kit that came with an already assembled PCB. The only soldering required was for the switches - the easiest part.
I understand what you're saying. I made one myself and I'm not really familiar with soldering or electronics at all..the instructions that come with are very very easy to follow. I'd say while yes it can get messed, because of the great docs the chance is definitely low. Just an idea of how new, this was my first time soldering anything..ever ! The best advice i can give, is to test the keys you solder while you go..but the docs already say that would be a good idea
Here's an instance where someone damaged their kit's microcontroller and was walked thru the repair process: https://old.reddit.com/r/MechanicalKeyboards/comments/5clvio...