Here's what the GSA does: Gives office space and 9 million $ to the candidate. What the GSA does not do: Give access to intel briefings or other agencies.
Biden now has an office and 9 million $, nothing more. President Trump controls his access to all other agencies and intel products. In short, Biden just walked into another trap. Every time the Fake News brings up the transition POTUS will say 'Hey, the GSA gave you office space and money'. The swamp walks into the trap every time.