4th Grade Math needs to teach Prime Factorization if it's going to be referenced

In 4th Grade Math, Unit 7 Lesson 2 "Finding common denominators", prime factorization is referenced: 1:47 "Another way that you could have found at least common multiple is you could have taken the prime factorization of six".
Is Prime Factorization taught before that lesson?  I tried searching for it (search term "prime factorization", limited to Content type: Article or Video, Domain: Math), and nothing obvious came up in the search.  I looked at every article and video that came up in the search that was from 4th grade or before, and did not find it taught anywhere.

Sal does a couple of examples of finding prime factorization in "Comparing and ordering fractions", but that is not teaching the general method, and it is not in any of the grade levels (as far as I can tell).

If a 4th grader watching the "Finding Common Denominators" video is confused about prime factorization, Khan Academy should have an easy way for them to find out what it is and how to do it.  Please add an easy-to-find teaching of prime factorization.

Also, I consider fixing the problems/holes/mistakes in the current curriculum and website as more urgent than adding new topics.  Does Khan Academy agree?