I was wrong. There absolutely is "engine noise" in SVS2. It exists roughly between 5 kHz and 10 kHz, and manifests itself as a prickly metallic sound.
This can be isolated (and removed) using the spectral dynamics feature in Pro-Q 4, but doing so also affects "sh" and "ch" sounds.
Like most unwanted noise, it is much more noticeable on pitched sounds (AKA vowels); and more noticeable on higher notes, and/or vocal databases that have more upper harmonics (AKA audible vowel harmonics that traverse across that 5 to 10 kHz noise zone).
Importantly, this noise is far far far more noticeable on SVS1 voice databases, although it still exists with SVS2 voices.
If anyone's interested in my Pro-Q 4 settings, let me know. However, it's not something I intend to use myself. First, it causes unwanted dampening of "sh" and "ch" sounds, necessitating automation to turn it on and off as needed. Second, my settings are not exactly a fine-tuned. It was just something I was messing with in an attempt to fix some harshness in Teto's C5 range. I will not fine-tune it any further, as this noise is less of an issue SVS2, so I'll just wait for Teto 2 to be released rather than fiddle with automation and whatnot.
Note: I still believe that source recording quality can be an issue. For example, the previously mentioned loud plosives found in the original Solaria SVS1 database. (I haven't tried the new version.)