I guess that you are referring to this new status icon:

Yours is one of many reports seen in recent days. This new icon appears to be undocumented by Apple at this time.
My own extensive testing has demonstrated this icon to indicate that a download to the iPad is occurring (you'll note from my screenshot that a download from a website is partially complete). When switching away from Safari to use another App, allowing the Safari to complete the download as background task, the new status icon will persist in view until the background download is completed.
Apple's documentation is often slow to catch-up with new features. Here is another status icon - that appears briefly when connecting some USB-C hubs - that Apple have yet to add to their documentation:
