From what I can tell the changes in the turbos, exhaust manifolds, downpipes, etc. are not actually significant. The fuel injectors, well that is different. But I still wouldn't say completely re-engineered.
Some info I found here:
https://f10.m5post.com/forums/showthread.php?t=1432202
Notable new parts include:
- New Engine Oil System
- New Intercoolers (Bigger)
- New Fuel Pumps and Fuel Injector designs which now pump at 350bar instead of 200bar in the F10 M5.
- New Turbos
- New Exhaust Manifolds for the Turbos
- New Downpipe Design