Catalyzes the conversion of 2-hydroxy-1,4-benzoxazin-3-one (HBOA) to 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA). Secondary metabolite biosynthesis; 2,4-dihydroxy-1,4-benzoxazin-3-one biosynthesis; 2,4-dihydroxy-1,4-benzoxazin-3-one from indoleglycerol phosphate: step 5/5. Belongs to the cytochrome P450 family.