This came with very little to no data available, and to be quite honest, saying “slow restore” doesn’t really mean much. The initial analysis needs to be an actual set of concrete data that describes the issue, what is normal, and what outliers, if any, exist. Since we have none, we can’t even start to analyze anything, so we need to clarify the problem statement and understand a little more about the issue.
This is an interesting dive into the problem and a good example of how to work with “We won’t let you see/do that” as a consultant. Incidentally, if you haven’t heard of WPR, that comes with the Windows Performance Toolkit.