Does ATC react to pilot position reports?
I controlled non-radar airspace for about 2.5 years.

On your end, we’ll probably just say “roger.” We may add instructions to report a future point, or a control instruction.

On our end, we would be using that information for any required separation. For example, we may update a flight strip with your groundspeed, recalculate how we anticipate bring traffic across that same point, or change how we are protecting airspace or altitudes according to where you are. It varies depending on the environment and traffic, but the general concept is ATC is protecting the entire block from where we last knew you were - your previous position report or where you were last in radar contact - and your next reporting point. Your position report allows us to modify that protected area.

But little to none of that information will be relayed to the pilot, unless it is operationally necessary. Even then, it will probably just be in the form of a control instruction.