I would imagine theaters that only had 2.0 capabilities played in 2.0 and those with 4.0 capabilities upmixed the 2.0 track to have surround. I mean even the original 2.0 are matrixed to Dolby surround (a more primitive form of pro logic) and I don’t see why they would go through the trouble of doing the matrix downmixing if theaters couldn’t handle it because I don’t believe people were using Dolby surround (pro logic) to watch movies at home until 80s or 90s.
So depending on the theater it was played back both ways?