There has never been a hard and fast limit on the number of requests that can be made via the News Search API. It has always been dynamically throttled. Since the deprecation, the throttle has grown more tight, but it remains dynamic. However, as you rightly noted, the API has been deprecated for more than 3 years now and may, therefore, be discontinued at any time. I would strongly recommend NOT building any new application on the API, and if you are working on an existing application, you will want to develop a plan to migrate to another service ASAP.
jg