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Paul, you are correct. It's more about preventing duplication in the software design rather than cleaning it up after the fact (which is an interesting problem, but a diff topic).

Think of it this way: one could build a detailed Entity Relationship diagram (or OOP equivalent) in a machine-readable format with all the relationship and column-size constraints defined. One could then push a button and have a machine generate a working version of the software. Those tools do exist. But they are usually missing useful details and result in UI's poorly tuned for how employees will likely be using the system.

Many of the tweaks to make it "practical" will be exceptions or local customizations to the original ER diagram data. Those customizations/deviations are the bottleneck such that in practice most stacks use duplication of info instead. See DRY ("Don't Repeat Yourself") in software engineering slang sites.