He compares the delay in unblocking or disabling the filter to traditional delays associated with requesting materials from closed stacks or interlibrary lending practices.
Also, for some reason, interlibrary lending never did pick up in India (and most other parts of the developing world).
The trickiest one I've had in recent years was the house research organ of a New Zealand medical school, but an interlibrary search turned it up.
My first Quabalah book had to be interlibrary loaned.