IMO whether or not you actually use maths you learned in school again, the act of having learned the maths established a wiring in your brain that didn't exist before. and it's the wiring in your brain that makes you a better problem solver
2 unit isn't advanced mathematics, 4 unit is :D
If you did 5.2 maths in stage 5 then doing mathematics would be difficult anyway if you hadn't caught up to the 5.3 work.