That's mostly but not strictly true, possibly depending on your definition. One example of analog encryption would be there was a system around WWII times where noise from a phonograph was added to a call to avoid evesdropping, and then on the receiving end it was subtracted out using a specially synchronized phonograph.
Another that I'm not sure on exactly, but back when TV was analog, there were some channels designed not to be watchable without paying. Not sure how those worked, it may technically qualify.
The analog TV stuff isn't encryption, it's scrambling. Those systems used proper digital crypto to generate the keystream, then scrambled video lines using a digital line buffer. They aren't secure (you can decode the picture by correlating lines without having the key) and they still rely on digital bits to do the processing, even if the image itself is transmitted as analog.
So no, analog crypto doesn't exist, though you can certainly obfuscate analog signals in various ways. For crypto to be analog the actual cryptography would have to be performed in the analog domain. To my knowledge, that doesn't exist and can't exist.
Another that I'm not sure on exactly, but back when TV was analog, there were some channels designed not to be watchable without paying. Not sure how those worked, it may technically qualify.