Not the whole story. That 1.5v is for single core only use, when using multiple cores it's advised the cpu not exceed 1.26v at boost for any length of time. Early OCers found that out the hard way in early OC attempts when cpus were burning out in less than 6 months with constant voltages of 1.35v - 1.4v ish range.
Did you read the article I linked? The behaviour that AMD's Robert Halleck describes is pretty much that. His response to 'what's a safe voltage' has been fairly consistent: safe is to leave it in AUTO, and when in AUTO you'll see it going as high is 1.5V and in the 1.2 to 1.3 volt range during heavier loads. And more: it will drop to as low as .6V when in sleep states (which is amazingly often, even in the midst of heavy workloads).
Also, saying '1.5V is single core only use' is a bit misleading as Ryzen does not have core-specific voltage. Ryzen boosts a single core only in a lightly threaded workload to as high as it's max boost clock and might need as high as 1.5V when doing it. When it spikes the voltage, all cores will have to see it. Early on an overclocker, TheStilt, wrote that Ryzen does not have functioning LVDR's on the die. You'd need something like an LVDR on die to lower voltage from the single VCore voltage feeding the CPU. I've not read where anybody has suggested that's changed, although there was some discussion it might be different on Threadripper.
It's unfortunate but we have to live with dribbles of good stuff of the sort we get from Robert Halleck, and what little some enthusiasts (TheStilt, Buildzoid, 1Usmus, Der8auer are notables) can gleen from their analysis of CPU's, BIOS code,and leaked engineering data. It seems anybody who gets good information from AMD is also silenced with NDA's. That's been one of Buildzoid's complaints as he said he could ask AMD for more info but he'd have to sign an NDA and then he'd probably not even be able to share what he finds out with his experiments for fear of tripping the line. AMD has to loosen up a little bit and share more info with the enthusiast and DIY community so we're not all left speculating. This all goes to OP thinking he 'really needs to lower' voltage when it's perfectly normal going to 1.5V when it boosts.