"Last Inventory Update" field not very useful?

If you are doing anything with the API that touches those records, the inventory update will show the date of that API call. So if you're updating anything on the record today, the last inventory update will reflect today's date.

If you have an integration or app (like MUT) that is updating extension attributes or other various data on the Jamf record, using the API, it will also update the Last Inventory Update value.

In a limited sense, if you only cared about when the Jamf binary successfully updated inventory locally on the machine, then I can see your point. But otherwise, it is valuable to know when the inventory data was updated from any source. If you want to know what Macs are active in your environment, I suggest using Last Check-in instead, or a combination of both.

This occurs solely due to the API for updating the computer record information.

It's crucial to identify the API account or API Client that updated the computer/mobile device inventory and disable it to mitigate potential security risks.

You can verify this information by clicking on the History button of the specific computer inventory or by reviewing the change management logs