"Players will now be able to experience the full seamless multiplayer features: Nearby bounty targets and Prime_Eight rivals will join the player's world for them to hunt down and hack without going through the Multiplayer App in the smartphone. Players will also encounter friendly Dedsec hackers who can help them complete different Dedsec events throughout San Francisco. Players can also invite those Dedsec hackers to form a co-op team and complete co-op missions."
During the pre-launch period when press had advance access to the game, Ubisoft discovered that the drop-in multiplayer was wreaking havoc on Watch Dogs 2's frame rate and general stability. While certain multiplayer modes were available before this patch, as the statement says, you had to set them up for yourself rather than randomly happening upon another player in your own world -- a step back from how the first game worked.
Watch Dogs 2 was released on November 15th, so if you're keeping track at home, it took just over a week for the patch to make it through Microsoft's and Sony's respective quality certification programs.