While I have seen a few references to Bubinga that call it "African Rosewood", I've read many others that state it is not a "true rosewood" and/or it is truly a completely different species of wood with different grain patterns as well as sonic qualities when used in instruments (likely not entirely relevant as headphone cups). Example: http://www.sheppardguitars.com/bubinga.htm
Since Audeze themselves sells a variant of the LCD-2 as "Caribbean Rosewood" and the LCD-XC as "Bubinga", I mentioned it, so people don't buy one and expect the grain to be a close match.
I own the LCD-3. The LCD-3 is often described as having tighter bass than the LCD-2. To my ears, the LCD-XC's bass is less forceful, but tighter and arguably more precise than the LCD-3. The difference is readily apparent, and not at all subtle. Neither is in any way shape or form, "boomy". So while your opinion may be valid, I don't think your opinion is in any way "more valid" than mine or x Relic x, to which you responded "No way, dude". FWIW, amplification used for comparison was Schiit Mjolnir and Violectric V200. I heard the LCD-2 on a Bryston BHA-1. Unknown revision.
It's not a point to be argued, per se. However, it's repeated so often that I think it's worth taking the opportunity to voice my opinion, the same way that you did.
I must say this is strange, I listened and compared the 2s and XCs for about a day. I definitely stand by my impressions, and what I heard is perfectly understandable as closed-back headphones generally get more resonant because of the bass being amplified by the acoustics. The bass of the XC I heard was definitely both heavier and less tight than that of the LCD-2 rev 2 (and, from memory, also the LCD-3)