A surprise for me here is that Fundamental VCO and WT-VCO don’t perform phase modulation. This explains why they sound so different from all the rest of the oscillators in my test patch.
The Fundamental VCO stalls when fed low enough voltage to its LFM input. WT-VCO doesn’t.
But both of them do respond to DC at their LFM inputs. That alone differentiates them both from all the rest in that patch (Kitchen Sink, NYSTHI operators, Bogaudio oscillators in linear FM mode, and Terrorform in default mode but not in True FM mode).