Indeed that is the intended behavior, each response is linked to a particular request and thus responses should not be mixed up even if several requests are made simultaneously. I would recommend you to look at some AI Predictions official documentation like:
In general, you should ask practical, answerable questions based on actual problems that you face (see, stack overflow How do I ask a good question? and What types of questions should I avoid asking?). Hence, try to implement your desired behavior and if you find any problems while doing so (e.g. responses are not properly assigned to each user) then let us know and we will try to help you.
In this case, if you find a clear issue with the Google prediction products you can open a public issue or contact Google Support so the Google team tackles it accordingly.