Final answer:
It's true that stateful packet inspection firewalls require additional processing to manage and verify packets against the state table, which can lead to performance issues.
Step-by-step explanation:
The statement that the primary disadvantage of stateful packet inspection firewalls is the additional processing required to manage and verify packets against the state table is true. Stateful packet inspection (SPI) firewalls maintain a state table that tracks every active connection passing through the firewall. They determine whether an incoming packet is part of an established connection by examining both the header information and the state of the packet, which does require more processing power compared to stateless firewalls that only look at the header information. This can lead to performance degradation, especially in environments with high traffic volumes.