I've read the same, and it seemed to be confirmed when I compared side-by-side the Minilogue XD's sawtooth to that of the Odyssey and Prophet '08. Definitely thinner, but also different in timbre.
The Minilogue XD I think is an amazing value. The timbral quality you refer to may be at least in part what I call "downmarket-signal-path-syndrome", which I do hear in the Minilogue as well as other synths that are in affordable pricing category, and even to some extent in pricier synths. It's a hard thing to describe but I feel like it comes from either the quality of the components in the signal path or the design of it or both, moreso than the raw tone of the oscillators. Sort of thin and slightly harsh at the same time. The best way I can describe it would be "artifacted harmonic distortion". It almost sounds to me like digital components getting in the way of a pure analog signal path, even if the culprit is not that at all. I even hear it sometimes on videos of the Pro3 and Take5, one reason I haven't taken an interest in either. And, having that quality doesn't mean a synth always sounds bad to me... I mean the Minilogue can sound great... it just means that on synths which have this "syndrome", I feel the range of sweet spots for which that synth sounds great (to my ears) are more limited, and they tend to put out a certain sonic vibe that makes me want to relegate the instrument to a duty that is not first and foremost in the mix as much as a backing instrument (for example I often use the digital oscillator of the Minilogue in combination with the sequencer for background movement).
I haven't quite heard that "downmarket vibe" in the MiniKorg 700fs vids I've watched, the overall tone seems pretty pure in most cases, but then again I have not really payed it a great deal of attention, simply because of the price and the fact that the control placement (which I think is fantastic for what it was originally designed for, resting atop a larger instrument like an organ) does not work for my particular setup. It looks fun, but probably not versatile enough for me to justify 2 grand.
Back to the Minilogue XD, I'm sorry to say that I may end up selling mine soon. The sequencer has always been one of the more compelling features for me, but my Keystep Pro gives me the ability to do everything the Minilogue does and more (in terms of sequencing) with any of my other instruments. The real reason I haven't let it go yet is because the custom oscillator capabilities are interesting, and may be reason enough to justify keeping it.
In terms of Asian synth production, I've often wondered if Roland/Korg synths preferred to keep the oscillators more precise and thin sounding, and fill the basic tone in with FX such as chorus. It's kind of a valid strategy, sometimes thinner core sound sources end up better once run through FX. The first analog I ever owned (Juno 106), ironically enough, stands out in my mind as a "fat synth", but admittedly a lot of that was from the Chorus, it was after all a single oscillator DCO synth.