Hi there kickerbeat,
We understand you aren't seeing the correct storage being reported with your Photos app on your iPhone, particularly after deleting the data in that app. There are a few things we will suggest to check. We'll be referencing this article as a guide: How to check the storage on your iPhone and iPad - Apple Support
Specifically look at the section titled "Use the Finder or iTunes to check the storage on your iOS device". Sync your iPhone to a computer to confirm if the data amounts are being reported correctly.
Use the Finder or iTunes to check the storage on your iOS device
1. On a Mac with macOS Catalina 10.15 or later, open the Finder. On a Mac with macOS Mojave 10.14 or earlier, or on a PC, open iTunes.
2. Connect your device to your computer.
3. Select your device in the Finder or in iTunes. You'll see a bar that shows how much storage your content uses, divided by content type.
4. Move your mouse over the bar to see how much storage each content type is using.
If storage on your device differs from what you see in the Finder or iTunes
Since the Finder and iTunes categorize cached files as Other, reported usage for Music or Videos might differ. To view usage on your device, go to Settings > General > [Device] Storage.
The other thing to check is if you have iCloud Photo Library enabled. Go to Settings > [your name] > iCloud > Photos. You will want to disable it to remove photos that could be synced from your iCloud account to your iPhone.
If the storage on your iPhone still shows data within the Photos app, and hasn't updated within about a day, we'd next recommend reaching out to our support teams directly. You can reach them here: Get Support - Apple
You can also find our phone number for your region at this link: Contact Apple for support and service - Apple Support
All the best.