I am surprised too.
However, one obvious competitor missed in this test is the Noctua NF-A12x15 PWM (chromax). How unfortunate. If this is included, this test will be more complete.
Using the manufacturer spec of these 2 fans as a baseline to compare, the Silverstone SS-120 fan has max 1800 rpm pushing 109 m3/h with 31.7 dBA (vs Noctua's max 1850 rpm producing 94 m3/h with 23.9 dBA). Interesting! Almost the same rotational speed but Silverstone is able to handle more flow (but, of course, generating more noise too).
Silverstone is listed at ~USD 8 (at jd.com and is much cheaper than Amazon's $19) while the Noctua is ~USD 22. Huge difference!
I am going to need four 120 slim fans for my COOJ Z13 build and I am currently inclined toward the Silverstone.