>If you watched the video you would have seen the purpose of why he built a laptop out of desktop parts. He built it so that he can have the advantage that a desktop has in a laptop form factor.
My BS filter is fairly time-tested by now, so the above never pass the smell test, let alone reaching the tire-kicking phase.
The laptop that was built is nothing more than a prop. A laptop by definition needs to be portable, ie being carried to different places. Said DIY-top would fall apart with the slightest handling.
The lid is epoxied together from 4 3D-printed pieces with no structural reinforcement. One finger pushing in the middle would be all it takes. The hinges are flimsy pieces that can scarcely bear the weight of the lid+display, let alone handle the rigors of repeated opening/closing. The unit has no battery, which reconverts it to a badly-built mini-PC. Basically, the unit is held together with bubblegum and duct tape.
But it looks nice, being painted for "accents" and logo and whatnot. Think that painted keyboard can stand up to repeated use?
In short, it's built for looks and YT consumption, ie for hits, not for any practical use. It's probably already being shoved into some dusty drawer, after the video upload, and will never again see daylight until the fateful house-cleaning moment, when it meets its ignominious end at some recycler.
At for the parts being used, they all have one commonality--they're cheap. RX6600 & 5600X are almost the cheapest parts that can still be labeled as "reasonably modern"--although 5600 would've been cheaper still.
The main function of these ventures, for YT creators, is to monetize, aside from building up their brand. Looking at the dude's small sub count (21K), keeping costs low would be a priority, as the end result--a janky prop--would be the same regardless of the parts. As long as the paint looks nice.