Why don’t iPhone Storage numbers add up in individual applications?

I was reviewing some storage numbers this morning and find some fairly huge discrepancies within some applications (especially Podcasts and Messages) when comparing the sum total to the individual constituent categories.

For example, the app size for Podcasts is 16MB. I have 369MB of episodes downloaded, and yet the Podcasts total Documents & Data rolls up to over 4 times that amount: 4.48GB.

Similarly, for Messages, I have 2.96GB in Top Messages, 2.24GB in Photos, 746MB in Videos, and less than 90MB in GIFs, Stickers, and Other, yet the total Documents & Data rolls up to almost double that amount: 9.8GB.

Is there “ghost” data hanging around? Is there a way to clear it out without deleting and reinstalling the app?