I’m really no expert, nor party to insider facts, but I thought DCOs produced/shaped the waveform in the same manner as as a VCO but that there was more control over tuning stability by deriving the frequency aspects from digital control rather than component activity. They’re both analog oscillators, but one is intrinsically more stable.
I’m not sure if the Analog Four is the same tech, but I’d surprised that Elektron didn’t then ask @smokyfrog to rephrase his review of their first Analog device to arguably enhance its prestige somewhat (he reviews the A4 as being a DCO synth) … also reiterated in this review here fwiw … One thing’s for sure, the RYTM does have tastier sounding open oscillators, but I’d been putting this down to other aspects
Perhaps though the need to keep the box powered up for 2 hours prior to calibration confirms that it’s indeed a VCO design as you’d obviously know in any case - curious to hear if anything’s different wrt the A4 and if the article raised eyebrows back then or whether it is a subtler delineation given that the marketing was all about digital control iirc