so by your own statement above, why would you take their recommendations on rebreathers if they are not experts? I wouldn't recommend any of the KISS units as a first rebreather and it has nothing to do with them being leaky valves, I just don't think the base design of any of their units are ideal for open water diving for most divers and they aren't "cheap" so it's not like you can get into it for $5k instead of $10k.
All of the KISS units are between $9k-$10k by the time they are ready to dive. The O2ptima, Liberty, JJ, etc. are all in that price range so it was one thing back in the day when the KISS units were half the price of the others, but they are now in the same price bracket so you have to ask yourself if they really are the best unit for you.
Anyone who spends that kind of money is going to try to justify their purchase and speak highly of it because it was incredibly expensive, just keep that in mind when you are listening to people talk about rebreathers. I'll be the first to tell you the things I can't stand about any of my rebreathers but they are the best compromise given my set of criteria for diving them, but there is no perfect rebreather out there and anyone that says so isn't qualified to have you listening to them...