Continuity mistake: Just after Millie arrives at the Pontipee farm for the first time, Adam pushes the closed cabin door open to take her inside. The shot cuts to an interior view, and Adam is opening the now completely shut door before walking in.
Continuity mistake: During the barn dance Frank's shirt front frequently changes between a V shape (like Ephraim's) and a U shape (Like Benjamin's).
Answer: Yes it is true. They did this to prevent the birds from flying into the backdrops and becoming injured or killed.