CPUs (x86 or PPC) only do out-of-order execution when it is provably the case that it doesn't matter. The result of running any given sequence of instructions in lock-step, or out-of-order should be exactly the same. If not, you found a CPU bug!
That said, timing matters in these tight inner loops, and that is where the details of the CPU pipeline matter, with respect to emulators. How many nanoseconds would it have taken for the emulated CPU to execute those instructions? That requires knowledge of how the CPU works. And sometimes, unfortunately, game code stupidly depends on these details.
With newer-gen high-level consoles and emulators, is that really the case? Having cycle/instruction accurate emulation only seems to be an issue for older consoles (PS2 and before?) where programmers actually relied on all sorts of things to eek out every cycle's worth.
That said, timing matters in these tight inner loops, and that is where the details of the CPU pipeline matter, with respect to emulators. How many nanoseconds would it have taken for the emulated CPU to execute those instructions? That requires knowledge of how the CPU works. And sometimes, unfortunately, game code stupidly depends on these details.