Separate components of the course (papers) have their own individual overall mark bands that can produce grade boundaries. However, because there are two papers the marks are added together as a percentage of the total, and a grade is created from that. Exam boards do not calculate grades for individual components in the real exams, they just go off the marks and then calculate the final grade at the end. So, say you got a superficial grade 5 on paper one and grade 7 on paper two, that would not necessarily equal a grade 6 just because 6 is in the middle of those two grades. You could just scrape a 7 because it goes of the addition of the marks of the two papers.
If you go to the grade boundaries section on the AQA website (not sure if this is available for other boards), it will show component grade boundaries (these grades will not be shown to you on results day) and overall grade boundaries (what will be shown to you on results day). This is what I have been told from some of my teachers who mark for GCSEs and a-levels for across multiple exam boards.
Hope this answers your question!