Apple Intelligence is downloading. Again? Why?

I'm finding that every few days the web page summaries feature in Safari stops working. It says "Summaries not available at this time. Try again later." When I check the Apple Intelligence section of System Settings I notice this message: "Apple Intelligence is downloading. Some Apple Intelligence and Siri features may be unavailable until the download is complete."

Why is it downloading again? Does Apple Intelligence download the entire LLM/knowledge base whenever there is an update from Apple? Is anyone else experiencing this?

Assuming that this is what is happening, it shouldn't render the existing features unavailable, surely. If Private Cloud Compute is to become a dependable feature in people's lives, it has to have 'availability' 'uptimes' equivalent to webhosting SLAs e.g. 99% uptime. If it effectively means you can't use it every third day, it's half-baked and half-arsed.