Dark Matter season 1 adopted the exact same rules about traversing the multiverse as the 2016 Blake Crouch novel of the same name. It was an incredibly faithful live-action adaptation of Jason Dessen's journey through countless realities as he tried to find his way home. However, because season 2 has no source material left to guide it, the multiverse rules have been forced to change to accommodate the next phase of the story.
With Crouch still showrunning the Dark Matter TV series, everything that's been added to the canon during the adaptation process has felt very authentic to the lore from the original book. That includes the new characters and storylines that are exclusive to the Apple TV sci-fi show. That being said, Crouch and company have made a notable tweak to how Dark Matter's various figures jump between alternate worlds.
FULL SPOILERS ahead for Dark Matter season 2 episode 2, "A Perfect World."

Somehow, Dark Matter's multiverse feels smaller in season 2
Dark Matter has always made it clear that being able to accurately pilot the Box is a difficult skill to perfect. It's a talent boasted by very few characters. Jason2 (Joel Edgerton) is very good at it, and Leighton Vance (Dayo Okeniyi) is also proving himself adept at jumping between specific universes in season 2. On the other hand, there's the overwhelming majority who are pretty much guessing their way between the countless realities with only a slender grasp of what they might find once they open the door.
Still, even with more new realities being introduced in season 2, Dark Matter's multiverse feels smaller and more accessible than ever. In the first two episodes, there have already been two separate instances of characters just happening to end up in the same universe as each other, despite taking very different routes to get there.
For example, the Dessens briefly stumble back into Futuristic Chicago at the end of episode 1, "A Quiet Life," where Amanda (Alice Braga) and Ryan (Jimmi Simpson) were then residing.
In episode 2, Amanda and Ryan happen to accidentally arrive in Retro Chicago, where the Dessens are building a new life for themselves. In neither instance do the two groups cross paths, but if this pattern continues, it's only a matter of time before they do run into each other. That's something that Dark Matter once led me to believe was all but impossible. While Amanda was reunited with her Blair (Amanda Brugel) in season 1's Giant Wasp universe, that was treated as an exception that defied the odds.

Why Dark Matter's change to its multiverse rules make sense
In season 1, Jason's attempts to reach his family and reveal Jason2 as an imposter were at the heart of the story. Therefore, it made complete sense that Crouch and company would make the multiverse feel like this impossibly large thing that couldn't be reliably traversed. Jason's journey had to be a massive uphill struggle, and it certainly felt like one. The other Box pilots were touched upon, but they didn't receive much focus.
Season 2 has been forced to alter its approach by the increased attention paid to characters like Amanda, Ryan, Leighton, and Blair. If the multiverse remained just as easy to get lost in, then all these characters would simply never cross paths. That's not great for this era of Dark Matter's story. As such, the show was forced to create the illusion of scale while also making it feel like the main characters are right on the verge of some pretty emotionally charged reunions. It's a smart move from a storytelling perspective, even if it dives into the very outer edges of retcon territory.

Dark Matter's smaller-feeling universe could be a subtle canon reveal
I think storytelling convenience is still the primary reason for season 2's lore update, but there could also be an in-universe explanation. The most obvious is that the Box pilots are simply becoming more experienced at getting where they need to be. Because everyone has similar goals, that could account for why everyone keeps just ending up in the same universe as each other.
Let's pair this logic with something a little more high-concept. We already know that the Box responds to its pilots' emotional state, thoughts, and feelings. All those things combine to influence which universe the Box pilots end up in next. This implies some form of telepathic element of the Box, which is a theory supported by the fact that a combined mindset of two or more pilots does make it trickier to find a universe that isn't absolute chaos — or unsavory in other ways.
Taking all of this into account, the fact that Ryan and Amanda are looking for Jason2, a person who ruined the Dessens' lives, could create some sort of cosmic connection between the two groups that is slowly drawing them closer and closer together. Crouch is the sort of writer who rarely lets details like these slip through the cracks, so I wouldn't be surprised if the Dark Matter author-turned-showrunner was planning to reveal that something like this is going on.
Dark Matter season 2 is streaming now on Apple TV.
