Practical impact has always been linked but ultimately independent of knowledge. You can have very sophisticated technology based on zero actual knowledge or understanding, like roman concrete or borosillicate glass. And you can have a very deep understanding without practical impact, like lasers for decades or galactic algorithms for multiplication.

Indeed, if a machine had told Heisenberg in 1943 (or whatever?) that "the critical mass for an atomic bomb is much less than you think", we could very well have had a different world today, regardless of Heisenberg understanding it or not.

> their practical impact can be independent of whether humans fully understand how they were reached

See: most of pharma

The problem is trading off short term and long term progress. A solution alone can be useful in the short term, but if humans don't also build up understanding it will probably prevent long term progress from happening. It's much more difficult to build on top of something you don't understand.