I don’t know, one way or the other. However, given the virtual instrument is branded as Yamaha, rather than Steinberg, and Yamaha’s long-term vocal synthesis product/technology is Vocaloid, I’d be surprised if there weren’t at least some technology underneath Omnivocal that has roots in Vocaloid. There was a discussion on this sort of thing in the Steinberg Lounge a few months back, and I gathered from that discussion that Vocaloid has progressed quite a bit over the years.
When watching the video demos Dom Sigalas did of Omnivocal, I noticed that, when he was entering English language lyrics, the result also displayed phonetic spellings that reminded me of what Vocaloid used to do. However, I suspect most any vocal synthesis software would need to do a similar thing. It made me wonder, though, if Omnivocal would allow overriding this, for example by entering the phonetic spellings directly. There are obvious cases where that could be necessary, such as in the case of heteronyms (i.e. words that are spelled the same but pronounced differently, such as in the case of bass, the fish, and bass the instrument or vocal range), as well as cases where it might just be desirable (e.g. for words two speakers from different backgrounds might pronounce differently – e.g. “Boston” by someone from Boston versus someone from most anywhere else).
I haven’t done anything with Vocaloid in a very long time (probably at least the late 2000s, if not a bit earlier). When I reviewed Vocaloid MIRIAM for a demo, I know I’d use it to get a female vocal on an early demo of one of my songs. The only “production” use I made Vocaloid, though, was using Vocaloid LOLA (also from Zero-G) to subtly layer some background vocals with my own on one song (“Undertow” – it’s on all the streaming services). It is that latter type of use that most interests me at this point. (I really could have used it in a recording I did earlier in the year where I was trying to simulate a choir with just my own vocals. Not only were there issues of range, but also just wanting different timbres, where creative audio processing, even with tools like iZotope’s Nectar Backer module, fell short for achieving the results I was hoping for.)