That article confuses things worse than the usual over-simplifing article we find on the internet.
I think they're referring to what's more commonly called the FSB (for Front Side Bus, which is also a misnomer) clock. That's the clock 'standard' from which all other clock signals are derived on many platforms. That's frequently generated and, therefore 'governed' as the article says it, by the chipset (but not always...some motherboards use discrete programmable PLL circuits to do it). Since it is the reference for all the other clocks (CPU, memory, PCIe, SATA, etc.) if you adjust it up or down those clocks follow right along.
FSB may be called something else in different motherboard BIOS', including clock base, but never base clock. As you note, the base clock is intrinsic to the specific CPU and as such is part of the CPU's warrantied specifications so you can never change it. With Ryzen it's the lowest rated clock the CPU will perform at under maximum all-core loads with capable cooling and running under stock settings. It might be forced to run faster (in similar conditions) than it's base clock when you overclock but the rated base clock speed is still the rated base clock speed no matter what.
Interestingly: Ryzen's boosting is so temperature dependent that just using high-end cooling can force the processor to run much higher than it's rated base clock under maximum load conditions with default stock settings. For instance, my 3700X drops back to very nearly it's rated base clock (3600Mhz) under it's stock Wraith cooler in Prime95. Just putting it under a 240mm AIO cooler and it runs 300Mhz faster...3900Mhz...in the same work load with the same settings. So, is that overclocking?