Bit late to party but when I did my apprenticeship many moons ago. Once you had the basic cube which had to pass both size and surface finish. The next step was about loading and unloading a 3 jaw and 4 jaw and then how and why you centralise work and clamping work off centre. But saying that I can appreciate the time saved clamping it in a split tube.
As we haven't got a 4 jaw chuck it wasn't an option but I can see how it works as another learning step in the process.