When doing a journal bearing design, the viscosity and flow rate of the oil is part of the design package.
And of course so is clearance, width, diameter....
It's also a specific oil spec, DexosD, which currently only have 2 approved/licenced oils.
https://www.gmdexos.com/brands/dexosd/index.html
Brand Name......................Supplier....................Specification.......Viscosity....License Number.....Region
ACDelco Light Duty Diesel...General Motors...........dexosD™️...........0W-20......DD0751IA015........Global
Mobil Super 3000 XE2.........ExxonMobil Oil Corp....dexosD™️...........0W-20......DD0752IA015........Global
This is NOT the same oil as recommended for a 6.6L.