Okay... some good news. The insulation I was seeing before was just some leftover blanket wrap remnants that the installer shoved up around the outside of the liner, to help insulate / seal off the block-off plate. I pulled it out, and the liner looks like a good install. However, there were many hand-sized chunks of the light puffy creosote, and I'm not sure where they're coming from. How could they be between outside of blanket-wrapped liner and my clay tile chimney? They're too big to have been there during install.
Found a label from the appliance adaptor or liner up there... still partially legible. Guess it's not getting too hot in there.
Found a label from the appliance adaptor or liner up there... still partially legible. Guess it's not getting too hot in there.