I also have a newer batch Ryzen 3600 and while my stable overclock is a "measly" 4400 mhz @ 1.337v (prime95 blend load), a CB20 I did @ 4.5 Ghz scored 4141 pts.
Now I really wish I had taken a shot of the heatspreader. Sounds like when I bought a recent new-batch 3600 CPU, that perhaps, I didn't really get a new enough batch. I think that the first part of the date-code was "19" and not "20", TBH.
I can't even get Windows 10 to boot on mine at 4.4Ghz all-core, even with a good bump in voltage. I'm at 4.20Ghz @ 1.3500V, something like that, that was required to be "PrimeGrid stable".
Edit: Or possibly, I need to step up to something with beefier VRMs than my Asus B450-F ROG STRIX Gaming ATX mobo, like an MSI B550 Tomahawk (my next board I'm eyeing).