If we are talking about a flywheel as an energy storage, low friction is a key component of its ability to store energy as a buffer. If this was not the case, the flywheel would lose its energy quickly on its own and the buffer would be gone.
> People love to use it to describe a forever growing thing, when it’s actually just a buffer.
A thing has other characteristics other than its intended purpose. Your assumption that you need to use intended purpose for a successful analogy is false.