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.

It needs to be mentioned that several players moved the laser to the other side of the Laserdisc, so you didn't have to flip the disc yourself.