An outcome from TM review.

In docs for UseCache/UseDistributedCache:

• This middleware doesn't guarantee that all data will be retained when responses are served from cache. Since we JSON-serialize everything for cache storage, we can only preserve things that round-trip through JSON.
• For example RawResponse objects will usually not be preserved
• Likewise, AdditionalProperties entries will usually be rehydrated as JsonElement values instead of whatever int/string/etc values they were originally

So altogether it's up to app developers to not rely on accessing data that can't be preserved through JSON serialization when using caching.