As a skill, I think it’s just called “engineering in a competitive market.” Anything you can do to make your chip more attractive to customers is a win, so designers go to great lengths to do so. Things like caches, pipelining, branch predictors, register renaming, out-of-order execution, etc. aren’t in any way fundamental to how processors work, they’re just tricks to make your program run a few percent faster. Designing a simple CPU in an fpga that executes everything in a single cycle and uses on-chip block ram is probably only a few hours of work for a novice. It would probably take you longer to download and install the fpga software!