I've said this in detractor streams/restreams/casts/whateverthefuckelse before, but I'd tread caution when believing what Subaru Man has to say wholesale.
No, he doesn't have a reason to lie about it since there's really no interest in him beyond looking for insight into Khet, but he also has no reason to make himself look bad, either. You're straight up hearing one side of the story, and, oftentimes in relationships, there's usually truth in both sides of a story as to why people split.
I know people have dug up dirt that may or may not be true about her past, but I'd still be apprehensive about believing everything the dude says. He's not going to make himself look like an asshole or divulge anything he's done that might be questionable. I mean, our favorite Horse-Lady left him for fucking Dave. The situation couldn't have been all sunshine and roses for that to happen, unless Dave is rocking like a 3 foot vibrating dick between his legs.
Just sayin'