Deleting photos and videos clears storage, but Photos app remains the same size. Anything I'm missing?

My Photos app is showing that it is 17gb in size when looking at storage in the general settings.

When I delete photos or videos (and remove them from the deleted items folder), I see the total storage size go down, so that is working.

However, I noticed that the photos app itself remains 17gb. Is this showing correctly, and is there a reason that the total storage goes down but the app size does not? Something to note is that it is backing up to iCloud but the cloud storage is full and I don't intend on expanding the iCloud storage. For this particular iPad, the photos are only for fun and I don't care if they are backed up. Thank you for any assistance!