It's true they are flying blind, but interestingly there was a whole story about PDB when Trump asked them to drop the CIA part of the PDB at one point. My limited understanding was that PDB is a double edged sword. If too many people are allowed to put stuff in their, it will change the message in the PDB and force the President to act in a certain manner, so not getting some of the PDB is actually a good thing.

I am pretty sure that whatever PDB that does reach Biden, is lovingly handcrafted by the White Hats to allow him to wander into the trap set for him each day.