I wonder if the devs chose that engine to work on or if it was kind of forced on them.
I remember reading about EA seemingly forcing a lot of their dev studios to use frostbite for a while. Bioware ending up creating ME:Andromeda with it, which was full of jank. Victory games reported a ton of problems with it trying to get it running an RTS (C&C Generals 2) as well and that game ended up getting binned.
Playground Games previously worked on the Forza series so it was probably the one they had the most experience with even if it needed some major tweaks