Oh god, please don't do this. This is worse than "We decided to go a different direction," because at least that takes less time to read.
If you're not going to provide substantive feedback ("we felt like your performance on the nearest-neighbor problem was pretty rough and were looking for a more optimized solution") then just give the one liner and be done with it.
We get it: you're hamstrung because of legal liabilities. That's fine. Don't make it worse by making us read a paragraph that isn't going to be helpful for the future.
If you're not going to provide substantive feedback ("we felt like your performance on the nearest-neighbor problem was pretty rough and were looking for a more optimized solution") then just give the one liner and be done with it.
We get it: you're hamstrung because of legal liabilities. That's fine. Don't make it worse by making us read a paragraph that isn't going to be helpful for the future.