Some good stuff in the videos. I prefer the "boring bar" method I think?
These videos show very well the principles involved, even if some of the details are a little imperfect.
Of course, as much as possible, stiffness of tools and workpiece and mounting is paramount to accurate machining. If things "move" use a smaller cut, slower feed, etc. until repeatable accuracy is achieved.
And be aware of maximum cutting speeds for the material.
I was taught "slowly, slowly, catchy monkey" - which also applies to repeatable accurate machining, especially of tougher materials like silver steel, or weaker, more flexible materials like aluminium. Often the most flexible part is the workpiece. Perhaps in the Hoglet aluminium demo it would have been better to have a bar at full size, instead of using the recessed grooves between the cams, then turning shafts down to size and the grooves after making the cams? If the original is a bar with centres in both ends, then this means the final lathe setting can be between centres and accuracy is maintained.
Please correct me if I have got this wrong? I'm just learning!