We are using Dynamic programming and you are correct, knapsack is a problem but since the most common solution(and widely used) is using DP, we sometimes intermittently use the term Knapsack algorithm with DP algorithm to solve Knapsack problem.
What would happen if I encoded a large integer factorization instance into a Knapsack Problem and called your system?
But it could as well terminate early, providing a suboptimal but fast solution.