Utilizing Intervals.icu online software, Coach Ryan Kohler reviews season-to-season changes in heart rate/power distributions, highlighting the ease with which you can determine if your training is hitting the appropriate energy systems by looking at training distribution.
He also reviews one of the intervals.icu graphs of the power/HR relationship to illustrate improvements across the different energy systems.
The take-home message? Know what you want to accomplish (e.g., what are your intended outcomes?) and use the appropriate tools/graphs to ensure accurate monitoring and actionable data so you can make adjustments if necessary.