Trust me I've been trying since I bought this CPU, the best I could do was 4.1Ghz all cores with tweaked PBO, this was on CB20, in daily tasks I could get 4300 in 3 cores, gaming between 4175-4350 depends on the game
Do keep in mind that boosting to a max boost clock (or over) is really just a 'feel good' kind of thing as I don't really think it adds materially to performance. So while mine boosts (some cores) to 4425 in light, bursty type tasks it's also doing it's real work, all cores, in 4.1-4.3 Ghz range. That's in a typical video rendering task or a CB20 MT benchmark run.
At 4.1Ghz during the BM it would be a lot like your your fixed OC, but mine will opportunistically boost to as high as 4.3Ghz when core temp and motherboard power margin allows. That's what keeping it in AUTO allows for, and that's why I get higher performance.
Also: how have you set up the system? My recommended keeps it pretty simple and probably what 1Usmus has you doing since I got it from one of his how-to's also. That's install the AMD chipset drivers and use the power plan they give you, then set Cool n Quiet, Advanced C States, Processor CPPC and CPPC Preferred Cores settings all to ENABLED. Leave core voltage and clock in AUTO.
Now, something I got from Buildzoid (an overclocker who degraded his 3700X with what he thought a safe fixed voltage), some simple set and forget settings for a tweaked PBO overclock. Enable PBO, in Manual mode. Set PPT to 330, EDC and TDC both to 230. Simple and it usually works pretty well for any system.
I set Auto Overboost to +200Mhz (that may not work for your mobo). I also set PBO Scalar to 5x; others say nothing over 1x as it maintains a higher core voltage than necessary which contributes to degradation but I can't see how that's happening. It may be my motherboard's not quite the same.
Last is cooling. Ryzen boosts higher/more frequently when it sees thermal margin, so better than stock cooling is essential. It will also boost less on warm days. That means when it's warm I get lower CB20 scores as it's may never boost above 4250 during a run.