It always confuses me when reviewers say stuff like this. I think I saw Joshua Valour say something similar once, about the Asgard 3 maybe? Something to the effect of "all solid state amplifiers should sound the same, otherwise something has gone wrong." Like, okay, the differences can seem subtle compared to the difference between headphones, but it all adds up in the end.
I was IN LOVE with the RebelAmp when I had it. I didn't find it to have crazy amounts of detail, like MaxSettings said in his review (compared with the Gilmore Lite Mk2 anyway), but I did find the mid bass slightly boosted with a really pleasant bloom, a slight rolloff in the sub bass, a sweet-sounding midrange, and with pretty non-fatiguing highs. The dynamic range was fantastic, but it just didn't have the impact I wanted, maybe because the increased soundstage made everything seem a bit farther away, so I eventually ended up with an FA-10 instead. A bit more pricey, but it definitely has the edge in imaging, layering, and detail, while the RebelAmp still had the bigger soundstage and warmer mid bass.
I can see why someone like Zeos would keep it around. It's a very fun and unique sound. I hope you get a chance to hear one someday!