It would make sense to share a trailer considering their two characters will “bond’ over some sort of unknown medical crisis that will plague Ian Harding’s character.
Perhaps Harding’s character suffers from PTSD and in revealing his past trauma they both realize they’re from a town where a bizarre murder took place?
The two are apparently “trailer buddies” on set, although we don’t know if that’s just a cute bit for publicity or they’re actually sharing a trailer.