Not gonna get into a pissing match, but you are incorrect. His is Poplar. The Charvel USA Collectors site with photos of the actual manufacturing specs prove it.
http://www.charvelusa.com/models.html
Uh, it would be nice if you linked me to the manufacturing specs, you just linked me to an enthusiast compiled spreadsheet.

Henrik's site (audiozone) is the exact same thing.
Not that is matters, just putting out there that you are using one site that doesn't have a definitive answer against the site I put forth that doesn't have a definitive answer. Like many others have pointed out, late 80s/early 90s Jackson/Charvels were doing a lot of funky stuff and switching around specs. Many of them didn't appear in catalogs. For example, people didn't know for years that the solid color 750xls were basswood (always assumed they were mahogany) until some started sanding them down. People didn't know that the early 90s Warrior Pros were 24.75 scale until they started measuring them. Etc.etc.
Unless the OP sands his down and sees the actual grain, he has to tell the difference with his ears. Recognizing the sound of a NT guitar (maple neck) with basswood wings isn't gonna happen for 99% of the population (myself included), since most people only know the bolt on Ibanez basswood sound. Poplar and Basswood can be equally heavy depending on construction, and the OP hasn't said exactly how heavy it is, so you can't really go on that.
I would say to the OP, if it sounds good, don't sweat it. Basswood gets a bad reputation from a lot of lower end instruments but a)650Xls are nice instruments, if it did use basswood it probably used a nice cut b)Maple NT w/ basswood wings is a completely different sound than what most people think of as "basswood guitars".
Hit up Lozek (over on mg.org,might be here too), he uses a bkp ceramic warpig (I know the OP was interested in BKPs) in his 650xl. He's posting in this thread;
http://www.metalguitarist.org/forum...ival-holy-crap-content-inside.html#post408802