Windows 7/10 for
2nd Gen AMD Ryzen Desktop Processor
7th-Gen AMD A-Series Processors
AMD Ryzen Desktop Processor
AMD X470 Chipset
AMD X370 Chipset
AMD B450 Chipset
AMD B350 Chipset
AMD A320 Chipset
Windows 10 only for
2nd Gen AMD Ryzen Threadripper Processor
AMD Ryzen Threadripper Processor
AMD Ryzen Desktop Processor with Radeon Vega Graphics
AMD Ryzen Mobile Processor with Radeon Vega Graphics
AMD X399 Chipset
AMD Chipset Drivers
AMD Ryzen Balanced Power Plan
That is not necessarily true. While they all conform to a base standard, they may be specific performance improvements, security and bug fixes contained in the proprietary driver. They may also be needed for proper raid function.
There are specific AMD RAID drivers available.
For non-RAID (plain AHCI) the old AMD AHCI driver (2015?) does not bring any performance improvements AFAIK.
Although the MS AHCI driver is dated "2006" it is more recent.
Regardless those are the reasons why you would load the proprietary drivers. Although I have seen many times over the years that those proprietary drivers either cause issues or are not necessarily faster so like most things, your mileage will vary.