I have an order update webhook firing and encountered a situation where an order was fulfilled using UPS where the tracking url just said 'https://ups.com'. Here is a clip of my data log showing the information I received:
Anyone know why this would be happening? UPS was a supported carrier as the shipment_status shows 'in_transit'. The tracking number is valid and shows that the package is in transit.
I just checked the order and it looks like the fulfillment was created with the URL http://ups.com explicitly provided. Since the URL was provided, it was added to the fulfillment as expected, Shopify only generates the URL automatically if one isn't provided. The tracking status updates based on the carrier name and tracking number, and since these are both valid this is why you saw the tracking status update.
This fulfillment was created by an app, and I'm seeing a similar URL on other fulfillments on the store. This URL is likely being provided to the app as input by the user creating the fulfillment, or has been saved as a "default value" in the app.