Technology, tends to be extremely finicky, and the more advanced said technology is, the more this generally tends to be true.
Here's my interpretation: Yes you can watch and record everything a Tinker does to make a piece of tech, but you'd have no idea why he's doing any of what he's doing. And this is very much a problem.
Let me give an example: You watch a Tinker install a gyro into a particular part of a high-tech bike, but no one but said Tinker would have any idea why that gyro is there. It could be that it's there for general stability, and every bike like it that the Tinker makes needs it. So you make the same (or as close to it as possible, given that there's no way to guarantee that it's absolutely exact given today's tech) gyro, put it in the same place, and you think it should work, right?
However, what if the Tinker placed it because the weight distribution due to metal makeup (minor metal impurities) makes the bike's center of gravity 3 mm lower than where it's supposed to be, and without the gyro to compensate, it'll quickly produce wear and tear in a completely different place in the bike, which will soon destroy certain essential functionality. However, if the balance was off a different amount, or is in a slightly different place, then said gyro needs to be either calibrated differently or placed in a different place to perform the same compensation.
Now, how's someone who doesn't know any of this, and only has the video of the Tinker putting the bike together, going to compensate for this? How would they even know that the center of gravity not what it's actually supposed to be?
And in an advanced, and most likely complicated, piece of technology, there's going to be hundreds, if not thousands or more parts exactly like that gyro. The Tinker would know what it's for, as well as where to place it and how to calibrate it to accomplish what it needs to let the machine work, but no one else does. How would anyone besides the Tinker in question know the difference between an essential part that needs to be in every bike and a piece to compensate for minor variances in manufacture (and there is going to be variances. Modern tech isn't good enough for it to be otherwise)?
So lets say that we also get the Tinker to record commentary on everything he does as he's making the bike. Then, when you're rebuilding, it happens that minor manufacturing differences resulted in a rotor contributing to a very small bit of vibration in another part of the bike. You might think it's harmless, but what if it actually isn't, and that the vibration is slightly beyond tolerance, and that it would cause fast degradation in some other part of the vehicle if it wasn't within tolerance? How would you know? It was easily within tolerance when the Tinker made his, so he didn't bother to comment on it. Thus, how would you know?
So, how can you do this? Are you going to get the Tinker to write out a manual on every single tiny detail that must be within tolerance, and do this for every part? Even if he writes up a 400 page textbook (which still might not be enough), it's quite likely that he might have missed one here or there, either just because he forgot or lost track (given that he'd be the only author, editor, and fact checker, it's quite likely), or because he just plain didn't think that something so unlikely would happen, but during manufacture, some dumb-ass would stumble across it anyways.
So yeah, that's basically what it's like for every piece of Tinker tech. There's a thousand different exceptions, with a thousand different variance for each exception, and a thousand different ways that it should be handled, depending on all of those thousand other exceptions and their thousand variances. Good luck trying to teach someone to work this shit. You'd have better luck trying to cram college level Calculus I down the throat of an elementary student who barely finished learning long multiplication. At least there, you'd know the theories behind it all, and can derive your way up to calculus. With Tinker tech though... Yeah, as I said, good luck...