My sources tell me that RIM originally outsourced much of the hardware design and production of the PlayBook to mega-ODM Quanta ... Amazon's own Kindle group (called Lab 126) apparently opted not to take on the project, in favor of continuing to work solely on next-gen E-Ink-based devices.
From there, Amazon's team determined they could build a tablet without the help and experience of Lab 126, so they turned to Quanta, which helped them "shortcut" the development process by using the PlayBook as their hardware template. Of course, it's never quite that simple, and as I'm told Amazon ran into trouble, and eventually sacrifices were made (like using a slower processor).
Although Amazon did refresh the ID of their PlayBook derivative, I'm told that this first tablet of theirs is "supposed to be pretty poor" and is a "stopgap" in order to get a tablet out the door for the 2011 holiday season -- which doesn't exactly leave the best taste in my mouth.
Bottom line: There's hardly any similarity between the two devices.
Now, just to make it clear, my intention here isn't to throw Ryan Block or gdgt under a bus. I respect Block and like gdgt, but instead it is to point out that rumors, even if backed by 'sources,' more often than not turn out to be nonsense. I know, because I get sent masses of nonsense my way each and every day. My job is to filter this, not pass it on to you in a raw, unprocessed state.
It's a fine line out there between fantasy and reality, folks.