Large Intune Win32 apps don't seem to cache

I was hoping to see one of our MCC's cache some large Intune Win32 app packages.  One is around 28GB and a couple of others are around 18GB. This is within Intune's Win32 app size limit. It's for a self-deploying Autopilot build and these are large sets of maps and documents. All packages deploy accurately given the download time needed.

We have 700 to build. The Internet service available at build sites is not really sufficient. An MCC seemed like the perfect solution.

Unfortunately, there is apparent evidence that the packages are not being cached. Not only do they not appear to register in the metrics, each device takes all day to build. Obviously, the more we try to do at once, the worse it gets.

Here is a screenshot of the metrics for the last 30 days:

This cache is dedicated to our PC Build Room's VLAN subnet. As you can see, Intune content only seems to account for 1.99GB when it should be much more than this. The MCC is 300GB in size.

Being able to diagnose why the MCC is not caching these Win32 app packages would be extremely useful. Is it our infrastructure or something else?

I have an open support case and also posted about it in the MCCP. Microsoft reps advised that MCC should be able to support these packages.