[blackflame7000]

It's not like DP is the only way to solve problems even designed for a DP solution. So an interviewee might have a general technique that applies for most problems but when faced with a DP problem their method takes more time. Now in an interview, taking more time is generally bad and this candidate would be judged lower. However, in real life scenarios, since DP problems are so rare, the interviewee's method might actually be faster.

Basically, giving any test question that is dependent on someone knowing something they could look up in a book is not as effective as testing how well someone reasons about an unknown type of problem.