I have consistently had this issue on my iPhone for years now.
My phone says I'm using 41 GB of storage with the Photos app and I have FOUR photos on my phone and two under-five-second videos. I've never used iCloud. I've troubleshot this with support a few times and did all the things they asked, most notably wiped and reinstalled everything. As it was explained to me (by a support tech who may or may not have been correct but the answer is plausible), even though the iPhone storage app says that it's showing you what is in the Photos app, the storage it shows for that app includes images from Messages as well so those images are counting double for your phone's storage for reasons that escape me. Would love to figure out a way for the iPhone storage to show up accurately. I finally got a phone with 256 GB because I was so tired of messing with it.
I know it's very uncharitable, but I think it's a real problem when the company who is trying to sell you more storage also has an odd bug in their system that incorrectly shows you are using more storage than you actually are.