[jimmyspice]

This assumes that once the design is done it should not, or does not have to change. Like anyone, designers can be wrong, customers can end up using certain features in ways not intended, and using software in ways that are not ergonomic.

So in that sense, design can and should be fluid. Where I work, designers often meet with customers (some external, some not) and continually get feedback, which the developers act on. IMO stopping design as soon as development starts increases the chance of having a poor design, forever.

Sometimes it's not known that a design has flaws until things start coming together during a project and some workflows become more prominent (and painful) than others.