Is there any reason why adobe would truncate the image requests? Is there a image request length restriction? We are using AppMeasurement 2.4.0 version and according to this article it should not truncate the request Handling Truncated Image Requests
I would recommend removing the image as it has some sensitive data.
As for the question. It is not truncating the data, but using a different method to send the data. When the image request is too large, the library changes the method from GET to POST. In the screenshot you have shared, you can see that the Request Method is POST.