The reason that weakening the rules around maintaining memory consistency can lead to increased performance is mostly because it can allow the hardware to reorder operations in a way that can hide memory latency. But, in doing so it can disrupt the expectations that programmers have when writing programs due to memory operations happening in unexpected orders which can result in unexpected values when reading and writing. So, we need to use synchronization libraries to place limits on hardware and compilers so that they do not reorder in a way that makes a program incorrect.
The reason that weakening the rules around maintaining memory consistency can lead to increased performance is mostly because it can allow the hardware to reorder operations in a way that can hide memory latency. But, in doing so it can disrupt the expectations that programmers have when writing programs due to memory operations happening in unexpected orders which can result in unexpected values when reading and writing. So, we need to use synchronization libraries to place limits on hardware and compilers so that they do not reorder in a way that makes a program incorrect.