In you example data in Output, imho, does not matching with BOM data.

B
C
D
1
 Parent desc Mat type Component
6
 Item 1 C
3.1
7
 Item 1 C
3.2
Sheet: Output

B
C
D
1
 Parent Desc Component Comp Desc
10
 Comp 4
3.1
 Comp 9
11
 Comp 4
3.2
 Comp 10
Sheet: BOM