Okay, did you file a bug on Github? Someone else may have more insight. I added some stuff to caching not that long ago (allowing caching with using custom vars), but I don't think I touched anything with disabling caching altogether.
Wait.... you cleared localstorage and still had cached files? That doesn't sound like Less.
It's possible you have long expiry's on your web host?
That is, it could be the browser/server that's not getting new files for you. The Less cache is stored only in localstorage.