If you take one photo and sha256 the a few MB jpg, I'm pretty sure that won't ever be reproduced. But you'll need to keep the file secure
It's 100% clear that the file has to be kept securely. The thing is that it's only you who will know which is the file (or files) needed for the seed. It can be stored on USB sticks, or even better, on cloud, without anybody knowing what's that for. I find it a not-so-bad way to store your seed.
With no checksum or error correction built in, it then becomes essentially impossible for the user in question to recover their wallet.
You are indeed very right on this. The user will have to keep the seed-source super safe. Even more, he will have to also keep super-safe the code that generates the seed from the source files and.. yeah, they should not be stored together.
It is an ingenious way imho. And some may like it. But it's also super risky, especially for really long term (like any non-standard way to keep the seed, after all).