The point isn't that they can be bribed, it's that the photographer has to attach their name to the photo and certify that it hasn't been altered or tampered with. It adds the ability to go after the photographer if they gov't ever discovers tampering has been done.
This is also where it is important to point out German culture.
Germans are extremely law abiding and rule following. People are also generally worried breaking social norms.
So while it is technically possible for photographers to digitally alter photos before upload, there will be very few who would dare to do that.
Photographers rely on the revenue from passport photos for their businesses to survive. Initially the plan was to exclude professional photographers too but the government backtracked on that after outcry.
New business model. Pop-up photoshop. Like the countless other businesses popping up, operating for a few months, washing money, closing down, owners gone, employees unknown, and so on.
Except it takes a while to start a business in Germany and there is lots of paperwork involved.
Also it sounds like licensing is required to be able to take passport photos. Chances are that licensing might apply to both the business and the individual photographer.
