Surely the masks and other doc are preserved in some form?
Apparently not, or at least, not the documentation. Maybe they have the low-level dies to make the chips from, but it sounds like no-one knows why the transistors are laid out that way. The company has changed hands multiple times, it seems.
For me it's interesting to see how (at least in part) the processor chip "works". I've often wondered what exactly happens at the chip level when it "executes" an instruction, and those talks make things a bit clearer.