Hey! I'm the owner of KeyboardLube.com and first of all, I would like to thank both you and your son for your order. I stumbled upon this thread when I was looking at my site's analytics and saw a pretty big jump from this site - figured I'd stop by and say "hello".
So, generally speaking, your son asked you to purchase this likely because it was recommended by either a Reddit post or a Discord conversation he was having with some others in the keyboard community. Generally (and I'm not just saying this because I own a store that sells it), Krytox 205G0 and other lubricants that I offer are considered to work great for their specific application. In this case, Krytox is actually manufactured by a large chemical company known as Chemours. In fact, 205G0 is more widely used in various industrial applications and it just happened to be discovered that it worked well for keyboard switches.
Is it needed? Probably not - but, in layman's terms, it nearly completely eliminates the "scratch" that you feel when you press down on a key. He's likely building a keyboard that's somewhere in the realm of $2-300 when all is said and done and he's probably after that "feel" that is considered to be success when you've completed your first build. There is indeed a use for it and it is almost completely noticeable and would not really consider it a waste. It's formulated in such a way that makes the viscosity perfect enough to improve the feel of a key switch but not limit it's ability to press down. In this case, the components of Krytox 105 is mixed (in a sense) with the components of base Krytox 205 - which is why you get 205 GRADE 0. It's created in a reactor which allows it to have an exceptionally long shelf-life and almost no separation which is hard to find in a grade 0 grease in some cases.
It's honestly a piece of a larger puzzle and - to be completely honest with you - it's probably the cheapest of components.
With that said, I'm happy to send your son some more for him (and you) to try in your blind test if you are interested. We offer a series of different lubricants and I can send him off with one of each. I'd implore him to try the different options and see what is best for his build because 205 might not necessarily be the best option for his particular key switch. In fact, if you have a keyswitch like blues, lubricant isn't even recommended at all. Just send me the order number that he was given when he placed his order and I will send it out when I get it from you. If he wants to reach me directly, I can send you my contact information via PM. All this "feel" talk is incredibly hard to explain with words but I would also encourage you to try them on a few switches yourself and see if you notice a difference between the lubricated ones and stock ones.
He'll learn a lot along the way. The lubricant piece is, again, a very small piece of the puzzle. He'll likely be learning soldering and a lot about electronics and programming. It's a fun experience that, quite frankly, I wish I've had as a kid.
Looking forward to hearing from you and also willing to answer any questions others may have as well. We're a pretty cool community and vendors are always ready to help - I'm happy he chose to be a part of it.
Best,
David