Callisa,
Going back in history, if you take a classic mini then a 20W50 was specified, but then it did chew improvers.
With more wear on start up perhaps with more stable oils 10W40 appeared to be standard recommendation and now M1 0W40 with HTHS of 3.6.
If a minimum HTHS of 2.6 is required to prevent excessive wear, this may only be ok if not using car after warranty period.
Honda may therefore specify a 0W20 for a high rev engine, however BMW found a problem with some engines and specified a xW60.
Somewhere inbetween may be a good compromise but we are limited by the Mechanical Engineers view of wear in the whole engine and protecting the weak spots.
Without guidance there appears to be a risk to move away from the manual for any particular engine.
Therefore can reducing viscosity and improving flow and temperature control make up for the higher protection provided by a higher viscosity and HTHS, and is it worth taking that risk and dropping viscosity?
The comparison is that WRC use a 5W40 but F1 use a straight 5 or 10.