Wood Database is a godsend for getting quality information on interesting woods, but trying to verify a vendor's claims about the identity and source of any given wood is hard!
One of the more interesting aspects of the business I learned there involved customs, ports of origin, and bribes. The difference between sustainable and/or organically sourced lumber has nothing to do with the lumber itself: it's about the bribe to the harbormaster. Can't get customs to release your barges of Russian birch? No problem, pay him/her enough and it's stamped as whatever you like it to be. You mentioned it was hard to verify the vendor's claims about the identity and source of a given wood, and that old job came to mind. I imagine in the supply chain, once far enough down, the vendor might genuinely believe they are selling you wood XYZ, because the wholesaler told them it was XYZ...but in reality, it all goes back to whatever they paid the harbormaster to stamp the export as.
PS: It's not that the harbormaster is the kingpin in this corruption. They are more like pawns...it was always presented to me as "the way business is done, since way back, everywhere". Just seems to be an accepted bit of dishonesty that everyone involved participates in and tolerates to a degree.
edit: typos