That really depends on a couple of factors really, like what type of appllication your using and how many programs you have running in the backround, How hot your VRMs are running under load and on what board chipset your at.
For example, Most of the times my 3900x also doesn't always run at 4Ghz in CB R20 as well, but if i turn off all backround tasks and really strip down windows (not ideal) it easily runs 4Ghz or sometimes 4.1 during CBR20. And on other benchmarks like 7zip benchmark i can reach even higher All core clock speeds regardless of how many apps i have running in the back, and this is on the new ABBA bios (of which i dont know yet what version your using) using the new v1.9.27.1033 chipset driver and a modified Ryzen balanced Power plan for even lower idle temps.
Honestly the easiest way to test if your CPU is throtlling using that Stock cooler is to use another/better Cooler for testing, something like a 240 AIO or a Decent Tower Cooler which is something you should be using anyways for something like a 3700x.
Those stock coolers are decent if your on a 3600-3600x but anything higher than that and your gonna start seeing temps like what your having, Its why most 3700x and up user usually opt to buy a better cooler and just resell the wraith coolers (which is quite pricy unused btw) that came with their processors. Even the old Hyper 212 Evo can beat the wraith cooler when it comes to temps (also less noisy) and you can buy those really cheap.
