Richard has done a great job of explaining that it is more than one cut but I'd like to add why.
The fact is that, even today, it's pretty much impossible to make a feature-length film in one cut... even with digital recording.
In the 50s, it was even more limited. All films were shot on actual film and filmmakers had to work around the limited length of the reel - either 500 or 1000 feet - which, at 24 frames per second limits directors to 11 minutes of shooting time per shot.
Modern digital cameras are limited in their shot length by the size of their digital media and the recording quality.
As an example, here's the stats for the Arri Alexa.
To paraphrase, with a 64 GB card, you'll get between 24 and 210 minutes of recording time depending on the codec you use. Now, 210 minutes is a really long time but the quality at this level would be very low. Some cameras may also have issues with overheating when used on very long shots and, if running on batteries, the batteries would certainly not last 210 minutes.
So, while possible (and actually accomplished in a 96 minute long Russian historical drama called Russian Ark), it would take some extreme measures to actually do it. For example, to limit the number of restarts, the director of Russian Ark recorded video only to avoid sound issues and recorded directly onto a large external hard drive that was able to hold up to 100 minutes of uncompressed high-def footage and had to be carried around with the camera.