I assume this means that The Wolf Among Us Season 2 is switching engines?
In case you're curious about "Why Unity?":
Multiple sources also tell Variety that the days are numbered for Telltale Tool, the company's in-house game engine. The studio is shifting to Unity for its projects (both detailed by Variety's source and referenced in job listings), with the final season of "The Walking Dead" the last to premiere on the old engine. "Stranger Things" is slated to be the first Unity engine project, according to multiple sources.
Sources tell Variety that while the move away from Telltale Tool is long overdue, a new engine means growing pains. Developers are re-learning how to manage workflow as they adapt to the new engine. This is causing a longer process than Telltale is used to working.
In case you're curious about "Why Unity?":
Source: https://variety.com/2018/gaming/features/netflix-telltale-stranger-things-deal-1202855424/