iPhone Storage - Messages section not showing list of Photos, Videos, GIFs

I have a bit of an odd situation. I was checking my iPhone Storage in Settings > General > iPhone Storage. I'm not running out of space, just keeping on top of space usage.

I noted that under the section "Review Large Attachements" it shows 2.28gb. Irritatingly, iOS doesn't show all attachments that make up the 2.28gbs. Only a limited number.

Anyway, when I then look at the list of apps, I see my messages app is taking up 343.6mb. But when I go into the Messages, it shows documents (photos, videos etc) totalling +/- 2.28gb. So that agrees to the "Review Large Attachments". But why doesn't the 2.28gb show or agree to the total for the messages app? Is the space used up by these documents / attachements included elsewhere, like in Photos?

But to make things more interesting, when I try to drill down into Photos, Videos or GIFs and Stickers from within the Messages section, there isn't anything in the list. Its just blank? Has anyone else had this?

I've done a soft and hard reset and no difference!