But I saw some benchmark videos on YouTube with R5 1600 af build. Then I found which motherboard was used in this benchmark and searched for cpu support list. There also was not 1600 af in support list.
Maybe because this cpu is released in 2019 and mobo manufacturers didn't updated the cpu support list?
Possible, but that is a risk YOU run. If you believe what you see on the Internet and want to try it, that is entirely up to you, but if you try it and it doesn't work, there's nothing anyone can do for you (except maybe a custom and unsupported BIOS update if one exists). You'd get no support from ASRock as they would simply say it's not supported.