Dual-layer DVDs didn’t come out until later. Long movies on single-layer (or those whose producers were too lazy to optimize compression or use dual-layer) DVD had to be flipped mid-movie as well.
Mass produced dual layer DVDs came out early on around late 1997 (maybe confusing with DVD recordable?), it’s not like the spec changed. There were some low cost distributors that couldn’t afford the equipment but the majors were stamping early on.
Besides unlike the one hour max on an LD, a 120 minute movie will fit on a single side single layer, so most early movie releases would fit on a single side single layer (the quality did suffer).
More commonly in the early days the dual side was to provide a pan and scan and letterbox option or extras.
There are so called “flippers”, but they weren’t that common.
An LD is 1 hour max so you are almost always flipping for any feature length.
With the dual layer discs, the first layer had to be larger than the second layer. There was a slight pause when switching layers, and care was taken to place the layer break at a spot to hide that pause as much as possible. At least on the discs where the author took pride in work unlike the YT decisions on when/where to place ads. Although, I've seen some really poorly placed layer breaks too.
Fun fact, I remember my french version of Reservoir Dogs switching from first layer to the other exactly during the torture scene, with the pause you are describing. Absolutely no care taken. Or maybe to put this at the worst moment possible. What a turn down !
I don't think they came out later. They existed in the spec from the beginning and some very early long movies were a single disc (e.g., Titanic). Some movies still needed flipping or two discs, like Gone with the Wind but it's just too long.
